Most clubs around here (Columbia, SC) pay the bands with the door charge instead of a percentage of the bar take. It's the fairest way really, the more people the band brings in, the more they get paid. When we play shows, we request this and set the door charge at $5 over 21 and $7 under 21. Works out well, the club gets all the money from the bar and the band(s) get the money from the door.

I suggest requesting the door charge thing when you play shows....even if the bar doesn't usually do this.