I like to offer the band to a promoter for a flat fee. If the promoter feels they might not be able to afford it, I offer them the chance of a guarantee much smaller than our flat fee, and a percetage deal which means we'll get our proposed fee if the turnout is reasonable. This seems to be fair. I don't like agreeing to a very low flat fee, when the promoter says" We can't afford much", because I've had my fingers burnt too often. Some club organisers have cheerfully admitted to me(unaware of quite what they were saying) that the low fee my band has charged has enabled the club to use the profits to pay more expeensive guests. Well, I'm afraid I'm trying to make a living, and I don't see why a promoter should depress my (low) earnings, in order to raise another performer's(high) earnings.
   I think a guarantee and a percentage deal is an excellent way for a finacially cautious club to afford the guests they want. I can't see any possible objection to the practise. Obviously, it's not the only financial model for running things, but it is one of several possible options.