Custom software vs SaaS: when it actually pays to build

“Should we buy a tool or build our own?” sounds like a technical question. It is almost entirely a business one. Build the wrong thing and you have created a liability your team maintains forever; buy the wrong thing and you have capped your product at someone else’s roadmap.

We help clients make this call constantly, and the honest answer is that most things should be bought. The interesting work is spotting the few that shouldn’t.

Buy your commodities

Authentication, payments, email, analytics, CRM — these are solved problems where a mature SaaS product is faster, cheaper, and more secure than anything you would build. Rebuilding them is not engineering ambition; it is expensive nostalgia.

The rule of thumb: if a capability is table stakes — something every company in your space needs and nobody wins on — buy it. Your engineering time is too valuable to spend re-implementing a login screen.

Build your differentiator

Now the flip side. If a workflow is your competitive advantage — the thing you do better than anyone, the reason customers choose you — a generic tool will eventually strangle it. Off-the-shelf software optimises for the average customer, and your advantage is by definition not average.

This is where custom software earns its cost. When the software is the product, owning it means owning your own pace of improvement instead of filing feature requests and waiting.

The hidden cost of both paths

Buying has a switching cost and a ceiling. Building has a maintenance cost that never ends — every custom system needs updates, security patches, and someone who understands it. We often land on a hybrid: buy the commodity layers, build the thin differentiating slice on top, and integrate them cleanly.

The decision is not “build vs buy” in the abstract. It is “for this capability, which choice compounds and which becomes a liability?” — asked one capability at a time.