Buy when
The problem is common and your process is not unusual.
- Accounting, payroll, email, storage, standard scheduling
- You'd be the only one asking for a feature nobody else needs
- The subscription cost stays flat as you grow
Build when
Your process is the competitive advantage, per-seat pricing is punishing you for growing, or you are paying three tools to do one job and gluing them together by hand.
The honest maths
Compare the one-time build plus a year of the maintenance plan against a year of subscriptions and the staff hours spent working around them. If the build does not win inside eighteen months, we say so.