Early in my career I found myself working at a mobile content provider on a PHP/MySQL app that was developed in Eastern Europe by a plucky but perhaps not the most best practice oriented entrepreneurial developer.
A rather large business had been built on top of this platform and it was suffering from the strains of scaling (revenue was in the multiple millions by this point).
One day, I was working on some code clean up and refactoring to improve some functionality in the billing piece when I realized there was an error in the logic that would cause the customer to be double-billed for each piece of content. I dutifully filed a ticket for the bug, committed a fix, and deployed it to production.
In less than 2 hours, our sysadmin had rolled back my fix and the ticket changed to closed, won't fix, as the impact on the company sales projections was too much... I didn't stick around long after that!