I seem to remember Bruce J. posting on the BBB board that the band varies their fees depending on the gig. For example, they might not get as large of a fee for playing at a private party as for playing at a bigger venue. The difference in ticket prices might reflect how much more money the band is making from place to place, not the venue making more money off them.
Yeah, I've got three mike/buce shows coming up this year and there is about a $20 difference for each one...but look at the venues...
$75- Pier Six Pavilion- Straight M&B concert
$45- Great Frederick Fair-County Fair...LOTs of other things happening.
$35- The Inlet Parking Lot at Sun Fes- This is just a seat. I could stand on the other side of the fence and hear/see the band fine.