Only the bride and groom have the power to tell me to change the song immediately, and even then, I've only had that happen with either the occasional drunk bride who is kidding around or one who can wait until the end of the song.
As I reviewed this thread, I was amused at how many would actually have taken the money and changed it up.
If this situation had ever hit me at a wedding reception, I'd simply look at Jon (J Mac), he'd look at me, and we'd both be thinking the same thing: Absolutely not.
When I play a song, I play it for a reason. If the bride and groom and 70+ other people are having fun, why change it up? $1000, $1M, not even $1B would do it for me. In my opinion, the guy can keep his money, the request will be written down, and I will try to work it in if it's not on the DO NOT PLAY list. Plain and simple.
EDIT: What I mean is this: I will not be bought out.