Build vs Buy: The Framework That Saves SaaS Founders $100K

The Decision Every SaaS Product Faces

You're building a SaaS product. Here's the question you face for every feature:

Should we build this ourselves or buy an existing solution?

Email: Build custom or use SendGrid? Payments: Build custom or use Stripe? Auth: Build custom or use Auth0? Analytics: Build custom or use Mixpanel? Support: Build custom or use Intercom? Hosting: Build custom or use AWS/Vercel?

The answer isn't obvious. And getting it wrong costs money.

The Framework

Before deciding build vs. buy, answer one question:

Is this capability a source of competitive differentiation?

If yes: Build. If no: Buy.

That's the framework. Everything else is details.

What This Means in Practice

Build When: It's Your Core Value

What you build should be what makes you different. What competitors can't easily replicate. What customers come to you for.

If your SaaS is a project management tool, the project management part is build. The email notifications are probably buy.

Buy When: It's Infrastructure

Infrastructure is rarely a competitive advantage. Email delivery. Payment processing. Server hosting. Authentication.

These are solved problems. Use the solutions.

Buy When: The Problem Isn't Yours to Solve

The best SaaS products focus on one problem. They don't try to solve every adjacent problem.

If the problem isn't central to your value proposition, buy the solution.

The Decision Matrix

Here's how we evaluate build vs. buy for client projects:

Score each factor. The pattern tells you what to do.

Build pattern: High differentiation, high customization, you're willing to own maintenance

Buy pattern: Low differentiation, low customization, you want to focus on your core product

The Categories

1. Always Buy

These are solved problems. No reason to build.

Payments: Stripe, Paddle, LemonSqueezy Email delivery: SendGrid, Postmark, Resend Auth: Auth0, Clerk, Supabase Auth Hosting: Vercel, Railway, AWS Error tracking: Sentry Analytics: Plausible, Mixpanel, PostHog

Building these yourself is reinventing the wheel. The buy solutions are better and cheaper.

2. Usually Buy, Sometimes Build

These depend on your specific needs.

Customer support: Intercom, Crisp, Plain Landing pages: Carrd, Webflow, Framer Video: Mux, Cloudflare Stream, Vimeo File storage: AWS S3, Cloudflare R2, Supabase Storage

Start with buy. Migrate to custom if needed.

3. Usually Build

These are core to your differentiation.

Core product features: The thing users come to you for Custom workflows: Proprietary processes that differentiate you Data model: Your specific way of structuring information User experience: How your product feels and works

4. Always Build

If you're building a tool in this category, you're probably wrong.

Basic CRUD: Any standard database operation Standard forms: Input, validation, storage Basic dashboards: Standard data visualization

The Real Cost of Building

When evaluating build vs. buy, consider the full cost of building:

Direct Costs

• Development time
• Testing time
• Documentation
• Ongoing maintenance

Indirect Costs

• Opportunity cost (time not spent on differentiation)
• Bug risk (yours vs. established solution)
• Security risk (yours vs. battle-tested solution)
• Scaling cost (you pay to scale vs. predictable vendor pricing)

Hidden Costs

• Time to market (buy is faster)
• Engineering morale (maintaining infra is boring)
• Technical debt (building things that should be simple)

The Buy Math

Let's say you're evaluating building vs. buying an email solution.

Building:

• Development: 3-4 weeks
• Testing: 1 week
• Maintenance: Ongoing (upgrades, deliverability, spam issues)
• 3-year cost: $50,000-$100,000 in engineering time

Buying (Resend):

• Integration: 1-2 days
• Cost: $20-$100/month
• 3-year cost: $720-$3,600

The math isn't even close.

The only reason to build is if email is central to your differentiation and the buy solutions can't do what you need.

The Build Math

Now let's say you're building a custom analytics system.

Buying (Mixpanel):

• Integration: 2-3 days
• Cost: $0-$1,000/month depending on usage
• 3-year cost: $0-$36,000

Building custom:

• Development: 3-6 months
• Testing: 1-2 months
• Maintenance: Ongoing
• 3-year cost: $200,000-$500,000

But what if your analytics is your core product? What if it's what differentiates you?

Then building makes sense. Because it's not infrastructure. It's differentiation.

The Questions to Ask

Question 1: Is this our core value?

If users would switch to a competitor if they had better [this feature], it's core. Build.

If users wouldn't notice if [this feature] was average, it's infrastructure. Buy.

Question 2: Can a vendor solve our needs?

Most of the time, yes.

If a vendor can do 80% of what you need, that's probably enough. The remaining 20% isn't worth building everything yourself.

Question 3: What's the maintenance burden?

Built things need maintaining. Vendor solutions need maintaining too, but you're not the one doing it.

If you build, you own:

• Bug fixes
• Security updates
• Scaling
• Feature additions
• Documentation

Is that worth it for this capability?

Question 4: How long does build vs. buy take?

Building takes months. Buying takes days.

If speed matters, buy wins.

Question 5: What happens if we get it wrong?

Building means you own the failure. Buying means the vendor owns the failure (and has SLA to back it up).

For critical infrastructure, vendor failure is usually less catastrophic than your own failure.

The Decision Tree

Here's a practical decision tree:

1. Is this core to our differentiation?

   • Yes → Build
   • No → Continue

2. Can a vendor do what we need?

   • Yes → Buy
   • No → Continue

3. Can we build it better than vendors?

   • Yes → Consider building
   • No → Buy

4. Do we have time/resources to build and maintain?

   • Yes → Consider building
   • No → Buy

Most decisions stop at step 2.

The Exceptions

Exception 1: Data Lock-in

If a vendor owns your data in a format you can't export, you're locked in.

For critical capabilities, prefer vendors that give you data portability.

Exception 2: Compliance Requirements

Some industries have specific compliance requirements. Vendors may not meet them. Build if vendor can't comply.

Exception 3: Ultra-Low Cost Requirements

If you're targeting a market where $20/month per customer is too expensive, vendor solutions may not work. Build cheap alternatives.

Exception 4: Unique Requirements

If your requirements are so specific that no vendor solves them, build.

The Anti-Pattern

Here's the build vs. buy mistake we see constantly:

Building infrastructure instead of differentiating features.

Founders spend months building:

• Custom email systems
• Custom authentication
• Custom analytics
• Custom payment processing

Then they wonder why their product has no users.

The features that differentiate (the actual product) got built with the leftover time and budget.

Infrastructure doesn't sell products. Core value does.

The Right Approach

For every SaaS product:

1. Map your capabilities: What does your product need to do?

2. Categorize each capability:

   • Core value → Build
   • Infrastructure → Buy
   • Supporting → Buy

3. Be ruthless about infrastructure: If it's not core value, buy it.

4. Focus engineering on differentiation: The hours you spend building email systems are hours you're not spending on your product.

5. Re-evaluate periodically: What was infrastructure at launch may need to be custom at scale.

The Summary

Build: Core value, competitive differentiation, unique requirements

Buy: Infrastructure, common problems, non-differentiating features

The goal is to maximize time spent on what makes you different and minimize time spent on solved problems.

Every dollar and hour spent on infrastructure is a dollar and hour not spent on your product.

Make the trade-off consciously. Build what you must. Buy what you can.

Want help deciding what to build vs. buy for your SaaS product? We help founders make these decisions as part of our technical strategy work. Let's talk. ",