Hey, there are a lot of people who have the same misconceptions as to what kind of low frequency requirements there actually are for live concert sound, and more than a few of them are in the pro-touring sound business. Even the pro-touring sound companies that really know their stuff typically will set up four times as many subs at a gig than are actually required. Why? Because the musicians and their tour managers insist on it, if only for the visual impact. The sound companies don't care if they're hauling extra gear and having to use more roadies than they need, they're being well paid for them. One more reason why you don't see $25 concert tickets.

Here's an RTA of ZZ Top in action.