When should a business build custom software instead of buying a product?
Build when the process is a competitive advantage or genuinely unusual, and buy when it is not. If your process looks like everyone else’s, a product will be cheaper and better supported than anything custom.
The honest test is what happens at the edges. Off-the-shelf tools handle the common ninety per cent well; the question is whether the remaining ten per cent is where your margin lives. If the awkward part — the approval that depends on three conditions, the pricing rule no vendor models, the compliance step that must be evidenced — is the part that matters, a product will push you into changing the business to suit the software. If the awkward part is just habit, change the habit and buy the product.