Not defending it but for clarity: it’s SQL Server Express that has the 10GB limit, and it’s free. They’re staying under that limit so they DON’T have to pay Microsoft. Aside from the Windows license, presumably.
Thanks for clarifying. Looks like the jump to standard is 989/year (if I'm reading Microsoft's confusing pricing sheet correctly). That's enough of a jump that it would definitely be a budget item for a lot of business. And migrating to a different DB engine isn't often an easy task, but keeping a DB maintained under a size limit sounds like a PITA and prone to accidental deletion of needed data. I definitely don't envy someone having to deal with that.