When is custom software worth building instead of buying?
Build custom when your process is a competitive advantage, when licence costs scale painfully with headcount, or when your team already maintains spreadsheets to patch the gaps in an off-the-shelf tool. Buy off-the-shelf when the process is generic — accounting and payroll are almost never worth building.
The honest test is simple: count the hours your team spends re-keying data between systems each week and multiply by a year. If that number approaches a build budget, custom software pays for itself.