Just for the record, I fully appreciate the concept of buyings CDs at concerts. I probably purchase CDs at about half the shows I attend. And if I know I'll be attending a concert in a few weeks for some artist that just released a new CD, I'll often put off buying that CD until I attend the concert, so that as much of my cash goes directly to the artist as possible. It's a very rare Black Cat show that I don't go home without at least one new CD. That said, the cost of the CD should be at least comparable to Amazon's price, for example. And don't forget that most albums can be downloaded for $9.99 via iTunes. A real CD with liner notes is worth a little extra to me, but anything more than $12 and I'm not buying basically.
I don't believe the assertion that Stars would have gotten all $15 if I had purchased a CD at the show. Surely, the 9:30 Club gets a cut of the merchandise sales? Someone has to pay the salary of the person who is staffing the merchandise booth. I suspect it's that cut which explains why CDs typically cost more at 9:30 Club shows than at Black Cat shows. CDs and T-shirts at Black Cat shows often seem to be sold by someone affiliated with the bands. At 9:30 shows, the merchandise booth is usually staffed by 9:30 Club staph, right? If so, the 9:30 Club has to be getting a cut of the merchandise sales. The Black Cat probably gets a cut too, but maybe it's not as high as the 9:30 Club wants?
[Edit: I see Kosmo posted practically the same information while I was in the midst of composing my message.]