Not me personally, but the company I started my career with (was an intern there for a few months). ERM software. When a new client comes onboard, install the product and database, but make sure not to make any optimizations, not even the basic indexes in the DB. Depending on the usage, the DB will get slower and slower in a few months. Then send a "consultant" who will simply run a script and add indexes etc and tes…
i wouldn't sweat it, a lot of economic activity is just information arbitrage.
Intentionally withholding stuff without offering an upfront option is shady though.