Buying software is often faster at the start, but off-the-shelf products can become expensive workarounds when your workflows are unique. The hidden cost is not the license; it is operational friction.
Custom software becomes the better option when process differentiation affects margin, speed, or service quality. In these cases, software should fit your operations, not force your operations to fit the tool.
A useful decision model compares five dimensions: strategic importance, integration complexity, data control, total cost over three years, and speed to measurable value. If most of these lean custom, building is usually the right call.