I'm not even sure that the general concert goer knows and fully understand how bands earn much more from a direct sale at a show, than through online purchases. The bands themselves should make this more known, usually the singer at a certain point has the mandatory "you can find our stuff at the merch boot" speech during a gig, but 30 seconds more to actually explain why, if you want to buy music, you might as well do it at shows, wouldn't hurt.