I'm pretty sure I had a mechanic (who had sold me one extra option and smelled blood) deliberately damage my sump plug in order to sell me an expensive repair.
The oil leak was slow enough that I took it to someone I trusted who re-threaded the sump to a larger size, fitted a larger sump plug and saved the oil into the bargain.
So yes, I'd say there are unethical everythings. Though I couldn't say that the service manager didn't lean on him to do it.