Custom software is expensive to build and expensive to keep, and there is a real point at which it stops costing more than the mess it replaces. That point is usually later than a vendor will tell you, and it has almost nothing to do with how many rows are in your spreadsheet.
The signals that matter are people re-typing data that already exists somewhere, a process that only one person can perform, and mistakes that have grown more expensive than preventing them. If none of those apply, we will say so.
