engineering-cost-model

Engineering Cost Model

Pre-Processing (Auto-Context)

Before starting, gather project context silently:

• Read PORTFOLIO.md if it exists in the project root or parent directories for product/team context
• Run: cat package.json 2>/dev/null || cat build.gradle.kts 2>/dev/null || cat Podfile 2>/dev/null to detect stack
• Run: git log --oneline -5 2>/dev/null for recent changes
• Run: ls src/ app/ lib/ functions/ 2>/dev/null to understand project structure
• Use this context to tailor all output to the actual project

Estimate the true cost of building, running, and maintaining software architectures. Use this before scoping projects, pricing engagements, or choosing between build vs buy.

Step 1: Classify the Cost Analysis Type

Need	Output
Project estimate	Total build cost (hours × rate + infrastructure)
Architecture comparison	Side-by-side cost of 2+ approaches
Infrastructure forecast	Monthly/annual cloud + service costs at scale
Build vs buy	Custom development vs SaaS/off-the-shelf comparison
Maintenance budget	Ongoing cost to keep a shipped product running
Client proposal	SOW-ready cost breakdown for consulting engagement

Step 2: Gather Context

1. What's being built — feature, MVP, full product, migration?
2. Platforms — Android, iOS, Web, backend, or combination?
3. Team — in-house, contractors, agency (rate per hour)?
4. Timeline — deadline-driven or scope-driven?
5. Scale expectations — users at launch, 6 months, 12 months?
6. Third-party services — Stripe, Firebase, AI APIs, CDN?

Step 3: Engineering Hour Estimates

Estimation Framework

Break every feature into tasks. Estimate each task in hours.
Always use three-point estimation:

  Optimistic (O):  everything goes right, no unknowns
  Likely (L):      normal development with typical blockers
  Pessimistic (P): significant unknowns, dependencies, or complexity

  Estimate = (O + 4L + P) / 6

Then apply the complexity multiplier:
  Simple (CRUD, standard UI):          1.0x
  Moderate (custom logic, integrations): 1.3x
  Complex (real-time, AI, payments):    1.6x
  Novel (never done before, R&D):      2.0x

Standard Task Estimates (hours)

MOBILE (Android or iOS — one platform)
┌─────────────────────────────────┬──────────┬──────────┬──────────┐
│ Task                            │ Simple   │ Moderate │ Complex  │
├─────────────────────────────────┼──────────┼──────────┼──────────┤
│ Screen (UI only)                │ 4-8      │ 8-16     │ 16-32   │
│ Screen + ViewModel/State        │ 8-16     │ 16-32    │ 32-48   │
│ API integration (per endpoint)  │ 4-8      │ 8-16     │ 16-24   │
│ Local persistence (per entity)  │ 4-8      │ 8-16     │ 16-24   │
│ Auth flow (login/signup)        │ 16-24    │ 24-40    │ 40-60   │
│ Push notifications              │ 8-16     │ 16-24    │ 24-40   │
│ Payment integration (Stripe)    │ 24-40    │ 40-60    │ 60-80   │
│ Camera/media capture            │ 8-16     │ 16-32    │ 32-48   │
│ Maps/location                   │ 8-16     │ 16-24    │ 24-40   │
│ App Store submission            │ 4-8      │ 8-12     │ 12-16   │
└─────────────────────────────────┴──────────┴──────────┴──────────┘

WEB (Next.js / React)
┌─────────────────────────────────┬──────────┬──────────┬──────────┐
│ Task                            │ Simple   │ Moderate │ Complex  │
├─────────────────────────────────┼──────────┼──────────┼──────────┤
│ Page (static/marketing)         │ 4-8      │ 8-16     │ 16-24   │
│ Page (dynamic + data fetching)  │ 8-16     │ 16-32    │ 32-48   │
│ Form (with validation)          │ 4-8      │ 8-16     │ 16-32   │
│ Dashboard / data table          │ 16-24    │ 24-40    │ 40-60   │
│ Auth (Firebase/NextAuth)        │ 12-20    │ 20-32    │ 32-48   │
│ Payment/checkout                │ 16-24    │ 24-40    │ 40-60   │
│ CMS/blog integration            │ 8-16     │ 16-24    │ 24-40   │
│ SEO + metadata + structured data│ 4-8      │ 8-12     │ 12-16   │
│ i18n (per additional language)  │ 8-16     │ 16-24    │ 24-32   │
└─────────────────────────────────┴──────────┴──────────┴──────────┘

BACKEND (Firebase / Node.js)
┌─────────────────────────────────┬──────────┬──────────┬──────────┐
│ Task                            │ Simple   │ Moderate │ Complex  │
├─────────────────────────────────┼──────────┼──────────┼──────────┤
│ CRUD API (per resource)         │ 4-8      │ 8-16     │ 16-24   │
│ Auth + security rules           │ 8-16     │ 16-24    │ 24-40   │
│ Webhook handler                 │ 4-8      │ 8-16     │ 16-24   │
│ Background job / scheduled fn   │ 4-8      │ 8-16     │ 16-32   │
│ Email/notification system       │ 8-16     │ 16-24    │ 24-40   │
│ File upload + storage           │ 4-8      │ 8-16     │ 16-24   │
│ Search implementation           │ 8-16     │ 16-32    │ 32-48   │
│ AI/LLM integration (per feature)│ 16-24    │ 24-48    │ 48-80   │
│ Data migration                  │ 8-16     │ 16-32    │ 32-60   │
└─────────────────────────────────┴──────────┴──────────┴──────────┘

CROSS-CUTTING
┌─────────────────────────────────┬──────────┬──────────┬──────────┐
│ Task                            │ Simple   │ Moderate │ Complex  │
├─────────────────────────────────┼──────────┼──────────┼──────────┤
│ CI/CD pipeline setup            │ 4-8      │ 8-16     │ 16-24   │
│ Analytics instrumentation       │ 4-8      │ 8-16     │ 16-24   │
│ Testing (per feature)           │ 8-16     │ 16-24    │ 24-40   │
│ Design system setup             │ 16-24    │ 24-40    │ 40-60   │
│ Project setup + boilerplate     │ 4-8      │ 8-16     │ 16-24   │
│ Code review + QA                │ 15-20% of total development hours       │
│ Project management              │ 10-15% of total development hours       │
└─────────────────────────────────┴──────────────────────────────────┘

Step 4: Infrastructure Cost Estimation

Firebase (pay-as-you-go after free tier)

Free tier covers:
  Firestore: 50K reads, 20K writes, 20K deletes per day
  Auth: 10K verifications/month (phone), unlimited email
  Storage: 5GB stored, 1GB/day download
  Functions: 2M invocations, 400K GB-seconds
  Hosting: 10GB stored, 360MB/day transfer

Typical monthly cost by scale:
  0-1K users:     $0-25/month (free tier covers most)
  1K-10K users:   $25-150/month
  10K-50K users:  $150-500/month
  50K-100K users: $500-2,000/month
  100K+ users:    $2,000+/month (optimize reads, use caching)

Third-Party Services

Stripe:          2.9% + $0.30 per transaction (no monthly fee)
SendGrid/Resend: $0-20/month (up to 100 emails/day free)
OpenAI API:      $0.50-15 per 1M tokens (model dependent)
Gemini API:      $0-7 per 1M tokens (model dependent)
Vercel:          $0-20/month (hobby/pro), usage-based beyond
Algolia/Search:  $0-50/month (up to 10K records free)
Sentry:          $0-26/month (error monitoring)
Analytics:       $0 (Firebase Analytics), $0-25/month (Mixpanel/PostHog)
Domain + DNS:    $12-20/year

Step 5: Project Cost Templates

MVP (one platform + backend)

Typical scope: 5-8 screens, auth, core feature, payments
Hours: 200-400 hours
At $150/hr: $30,000-60,000
At $200/hr: $40,000-80,000
Timeline: 6-10 weeks

Infrastructure (year 1): $300-2,000
Third-party services (year 1): $500-3,000
Total year 1: $31,000-85,000

Full Product (mobile + web + backend)

Typical scope: 15-25 screens per platform, admin dashboard, API
Hours: 800-1,500 hours
At $150/hr: $120,000-225,000
At $200/hr: $160,000-300,000
Timeline: 4-8 months

Infrastructure (year 1): $1,200-12,000
Third-party services (year 1): $2,000-10,000
Total year 1: $125,000-322,000

Maintenance (ongoing after launch)

Bug fixes + minor updates: 10-20 hours/month
OS/dependency updates:     5-10 hours/quarter
Feature additions:         scope per feature
Infrastructure monitoring: 2-5 hours/month

Monthly maintenance cost:
  At $150/hr: $2,250-4,500/month
  At $200/hr: $3,000-6,000/month
  Or retainer: flat monthly fee (typically 15-20% of build cost annually)

Step 6: Build vs Buy Analysis

DECISION FRAMEWORK

Build custom when:
  ✅ Core differentiator (this IS your product)
  ✅ No off-the-shelf solution fits >80% of requirements
  ✅ Data ownership/privacy is critical
  ✅ Long-term cost of SaaS licenses exceeds build cost
  ✅ You need deep integration with existing systems

Buy/use SaaS when:
  ✅ Not a core differentiator (auth, email, analytics, payments)
  ✅ Off-the-shelf fits >80% of requirements
  ✅ Speed to market matters more than customization
  ✅ Team doesn't have expertise to build + maintain
  ✅ Build cost > 3 years of SaaS subscription

Common build vs buy decisions:
  Auth:       BUY (Firebase Auth, Auth0) — never build your own
  Payments:   BUY (Stripe) — never build your own
  Email:      BUY (SendGrid, Resend) — commodity
  Analytics:  BUY (Firebase, Mixpanel) — commodity
  Search:     BUILD if simple, BUY if complex (Algolia, Typesense)
  CMS:        BUY if content-only, BUILD if integrated with app logic
  AI features: BUILD (custom integration with LLM APIs)
  Core logic:  ALWAYS BUILD — this is your product

Live Pricing Data

Use WebSearch to fetch current pricing for infrastructure components:

• "Firebase pricing calculator 2025"
• "Vercel pricing tiers 2025"
• "OpenAI API pricing per token 2025"
• "Stripe payment processing fees 2025"

Flag any assumptions that differ from current published pricing.

Scripts

This skill bundles a stdlib-only script under scripts/. Supports --help and --json. See docs/SCRIPTS_CONVENTION.md for the contract.

• scripts/cost_estimator.py — Total project cost from --hours, --rate, --infra-monthly, --duration-months. Includes PM/QA overhead and optional contingency.

  python3 skills/engineering-cost-model/scripts/cost_estimator.py \
    --hours 400 --rate 175 --infra-monthly 250 --duration-months 6 \
    --pm-pct 10 --qa-pct 15 --contingency-pct 15 --json
  

Step 7: Cost Estimate Output

ENGINEERING COST ESTIMATE
Project: [NAME]
Date: [TODAY]
Prepared for: [CLIENT]

SCOPE SUMMARY
  Platforms: [Android / iOS / Web / Backend]
  Features: [list key features]
  Timeline: [X weeks/months]

DEVELOPMENT COST
┌────────────────────────┬───────┬────────────┐
│ Component              │ Hours │ Cost       │
├────────────────────────┼───────┼────────────┤
│ [Feature 1]            │ XX    │ $X,XXX     │
│ [Feature 2]            │ XX    │ $X,XXX     │
│ [Feature N]            │ XX    │ $X,XXX     │
├────────────────────────┼───────┼────────────┤
│ Testing & QA (15%)     │ XX    │ $X,XXX     │
│ Project Management (10%)│ XX   │ $X,XXX     │
├────────────────────────┼───────┼────────────┤
│ TOTAL DEVELOPMENT      │ XXX   │ $XX,XXX    │
└────────────────────────┴───────┴────────────┘

INFRASTRUCTURE (YEAR 1)
┌────────────────────────┬────────────┐
│ Service                │ Annual Cost│
├────────────────────────┼────────────┤
│ Firebase / Cloud       │ $X,XXX     │
│ Third-party APIs       │ $X,XXX     │
│ Domain + DNS           │ $XX        │
├────────────────────────┼────────────┤
│ TOTAL INFRASTRUCTURE   │ $X,XXX     │
└────────────────────────┴────────────┘

ONGOING MAINTENANCE
  Monthly: $X,XXX (XX hours/month)
  Annual:  $XX,XXX

TOTAL YEAR 1: $XXX,XXX
  Development:    $XX,XXX
  Infrastructure: $X,XXX
  Maintenance:    $XX,XXX

ASSUMPTIONS & RISKS
  - [Assumption 1]
  - [Risk 1 — impact on cost if realized]

PAYMENT STRUCTURE (RECOMMENDED)
  30% — Project kickoff
  30% — Midpoint milestone (working prototype)
  30% — Delivery and launch
  10% — 30 days post-launch (bug fix period)