Some of the links on this forum allow SMF, at no cost to you, to earn a small commission when you click through and make a purchase. Let me know if you have any questions about this.
With a bag of charcoal and wood you could do a bunch of racks and cut you cost per rack down. He also pays less for the meat, and you'd save a ton if you make your own sauce and rub.
Ding, ding, ding! Winner! Exactly what DanMcG said. Not much you can do about charcoal and wood. For meat, you can look to the sources restaurants use, like Eastern Market here in the Detroit area. Might be able to shave some cost by getting closer to the source in the retail chain.
The other thing to consider is that if you're getting your meat from a good butcher you'll pay more, but you'll cook better meat than you'll see at a chain like Dave's.