Build vs. buy software: how to draw the line
- Ashit VoraBuyer's PlaybookLast updated on
Summary
Build custom software when the feature is your competitive advantage — the thing customers choose you for over alternatives. Buy off-the-shelf for commodity functions like auth, payments, email, and analytics that every company needs but none compete on. Buying saves 40-60% in year-one costs, but custom-built features that directly serve your core value proposition generate far more long-term business value.
Key Takeaways
Build what creates competitive advantage — the features customers choose you for
Buy commodity functions (auth, payments, email, analytics) — every competitor needs them too
Year-one cost of buy is 40-60% lower, but custom wins when it generates retention that SaaS can't
The real 5-year cost of a $200K build is $400K-$500K including maintenance — model this before deciding
Buy first to validate, then build once you know exactly what users need
Every successful software company builds some things and buys others. Stripe built their payment processing engine. They bought their office suite, CRM, and HR tools. The decision isn't build-or-buy — it's where to draw the line.
The line should sit between what creates competitive advantage and what doesn't. If customers choose you because of a feature, build it. If customers expect it but don't choose you because of it (auth, billing, notifications), buy it. This sounds simple, but founders consistently over-build commodity features and under-invest in differentiators.
We've seen startups spend 4 months building a custom auth system when Auth0 exists. We've also seen companies buy a generic CRM when their customer workflow is the entire product. Both are expensive mistakes. The build-vs-buy line is the most strategic technical decision your company makes.
Build what differentiates. Buy what doesn't.
Build vs. buy: side-by-side
| Factor | Build Custom | Buy Off-the-Shelf |
|---|---|---|
| Time to first deployment | 8–16 weeks for an MVP | 1–4 weeks for setup and configuration |
| Year-one total cost | $80,000–$300,000 for development | $5,000–$50,000 in SaaS licenses |
| 5-year total cost | $200,000–$600,000 including maintenance | $100,000–$500,000 in cumulative licensing |
| Customisation depth | Unlimited — it does exactly what you need | Limited to vendor's configuration options |
| Competitive moat | Strong — competitors can't buy your advantage | None — competitors buy the same tool |
| Maintenance burden | You own it — bugs, updates, security patches | Vendor handles maintenance and updates |
| Vendor risk | None — you control the code | High — vendor changes pricing, gets acquired, shuts down |
| Integration flexibility | Build any integration you need | Limited to vendor's API and marketplace |
| Team knowledge required | Full engineering team to build and maintain | Admin-level knowledge to configure and manage |
| Data ownership | Full ownership — data stays in your infrastructure | Vendor-dependent — check export and portability terms |
The case for building custom
What you get:
Fits your exact workflow — no compromises or workarounds
Becomes a competitive moat that competitors can't replicate by purchasing
Full control over roadmap, performance, and data architecture
No per-seat licensing costs that scale with team size
Integrates deeply with your existing systems without middleware
What you give up:
8–16 weeks to MVP vs. 1–4 weeks for a SaaS tool
$80,000–$300,000 upfront investment before you see value
You own maintenance forever — bugs, security patches, infrastructure
Opportunity cost — engineering time building a CRM is time not building your product
The case for buying off-the-shelf
What you get:
Ship in weeks — configure, integrate, deploy
80–90% lower year-one cost for commodity features
Vendor handles updates, security patches, and infrastructure
Proven at scale — thousands of companies have stress-tested it
Focus your engineering time on what differentiates your product
What you give up:
Your workflows adapt to the tool, not the other way around
Per-seat licensing adds up — a 50-person team at $30/seat/month is $18,000/year per tool
Vendor lock-in — switching costs grow with every year of data and process invested
Competitors buy the same tool — zero competitive advantage
When to build custom
Build when the feature is your product's reason to exist. If customers choose you because of how you handle a specific workflow, that workflow should be custom-built.
Also build when off-the-shelf tools force painful compromises — when you'd spend more time working around limitations than building the thing properly. Build when data sensitivity requires full control, and when long-term licensing costs would exceed development costs within 3 years.
When to buy off-the-shelf
Buy when the feature is table stakes that every competitor has. Auth, payments, email sending, analytics, CRM (for most companies), project management, monitoring. These features matter, but they don't differentiate you.
Buy when speed-to-market is critical and building would delay your launch by months. Buy when the vendor has spent years solving problems you'd spend months rediscovering.
The verdict
Draw the line clearly: build what creates competitive advantage, buy everything else. For most startups, that means building 1–3 core features and buying 10–15 supporting tools. Auth (buy), payments (buy), your core workflow engine (build), analytics dashboard (depends — buy for standard metrics, build for proprietary insights).
The companies that win build less software, but the software they build is the right software.
Frequently Asked Questions
- Two tests. First: would customers switch to a competitor who does this feature 20% better? If yes, it's core. Second: can competitors buy the same capability off-the-shelf? If yes, building it doesn't create a moat. Auth is never core (buy it). Your proprietary matching algorithm is always core (build it). The gray area is where product judgment matters.
- Plan for development cost in year one plus 15-25% annually for maintenance, bug fixes, and feature additions. A $200,000 build costs roughly $400,000-$500,000 over 5 years. Compare that to SaaS licensing at $30,000/year growing 10% annually — $180,000 over 5 years. Custom wins on value when it generates revenue or retention that the SaaS tool can't match.
- Yes — but only the one thing that makes them different. A fintech startup should buy auth, email, and analytics, but build their loan decisioning engine. An e-commerce startup should buy payments and inventory management, but build their product recommendation system. Early-stage companies have limited engineering hours. Spend them on differentiation, not commodity.
- It happens more than founders expect. Build with portable data formats and maintain export scripts. For critical vendors, keep a migration plan that estimates switching cost and timeline. The riskiest vendors are those with proprietary data formats and no export API. Always ask: can I get my data out in a standard format within 30 days?
- Absolutely. This is often the smartest sequence. Use a SaaS tool to validate the workflow and gather requirements from real users. After 6-12 months, you'll know exactly what to build — which features users love, which they ignore, and where the tool falls short. You build better custom software after you've lived with the off-the-shelf version.
