Build versus buy is one of the oldest decisions in business software: do you build the tool you need, or buy an existing one? The traditional answer leaned heavily toward buy, because building was slow, expensive, and risky. AI has rewritten both sides of that equation, and the calculation that made sense five years ago can lead you wrong now. Here's how to think about the new math.
The old math
Historically, building software meant a big team, a long timeline, and major cost and risk — so unless your need was truly unique and core, buying an off-the-shelf tool almost always won. Building was the expensive, risky path reserved for the rare case where nothing existing could possibly fit. Most businesses bought, sensibly, because building was simply too costly to justify for anything but the most essential, differentiated needs.
What AI changed
AI collapsed the cost and time of building software. What took a venture-backed team years can now be done by a small focused team in a fraction of the time and cost. That doesn't automatically tip everything toward build — but it means the old reflex "building is too expensive, just buy" is now an outdated assumption doing your thinking for you. The build side of the equation got dramatically cheaper, which means the decision deserves fresh consideration rather than the default answer.
But buy got better too
Here's the nuance: the same forces that made building cheaper also made buying better. The reason capable vertical platforms now exist for specific industries at small-business prices is precisely that AI-era development let focused teams build them. So the cheaper cost of building has, for many businesses, already been captured by vendors who built the deep, specific tool you'd otherwise build yourself — and maintain it, improve it, and support it so you don't have to. Often the smartest move isn't to build, but to buy the thing someone already built using the cheap-building advantage.
The new decision framework
The updated question isn't "build or buy" in the abstract — it's: does a tool exist that genuinely fits my specific business? In the AI era, the answer is increasingly yes, because vertical platforms now exist for niches that previously had nothing. If a tool fits your business deeply, buying it captures the cheap-building advantage without the burden of building and maintaining software yourself. You build only when nothing existing truly fits and the need is core enough to justify owning it. The math changed — but for most businesses, it changed toward "the right tool now exists to buy," not "build it yourself."
Don't let the old assumption that building is prohibitively expensive — or the opposite new excitement that anyone can build anything — make the decision for you. Ask whether a tool genuinely fits your business. Increasingly one does, built by a focused team using the same cheap-building advantage you'd be tempted to use yourself, and that's usually the smart buy.