I have bribed rebel towns a few times for 200,000-300,000, but never a general. Not sure I have ever tried though. It's a lot cheaper to raise an army and kill them.

And I believe the game is wired to make up general shortages by MOTH or adoption.

I do recall MTW bribery being a bit too easy - not so much for me but for the AI. I remember keeping low loyalty generals in seperate stacks from their armies, and combining them right before battles so that you didn't lose whole armies.