A smart hustler
always keeps a ball and a half for himself, so if he says he will give you the 7, he still figures he can beat you with the 6 ball. If he says he will give you 3 games on the wire going to 9, he still figures he can win giving you 4 games. A pro, or a smart hustler, is not there to donate money to you, especially in a cheap game. Spots usually go up, closer to even, when the bet is high.
This is one reason why many players prefer to play someone under their speed, or about their speed rather than someone that is decidedly better.
A couple of games still trying to get made that I have heard about lately:
A good regional semi-pro offering the break and orange crush to a low A player on the bar table for 3k, race to 15 or 21, forgot which.
(This A player played the set against a pro player, recorded all statistics to determine his chances for this bet, and the stats came out in favor of the A player). The good regional semi-pro backed out of the bet.
A good regional semi-pro (different one) offering 10 ahead set to Asian Snooker champion on a bar table for 2k. No jump cues allowed.