Yet many small business billing systems are basically an excel sheet with a word doc or manual online invoice system like square invoices. You wouldn't replace

Yet many small business billing systems are basically an excel sheet with a word doc or manual online invoice system like square invoices. You wouldn't replace a functioning billing system with this one, but you might not replace this one with an expensive custom system. As programmers, we often discount the value of our time to zero when we're writing software because it's kind of fun. But for a non programmer, 10-30 minutes of work each week invoicing isn't an issue if the system never gets into an unusable state.