I've been using 80/20 extruded aluminum for the past 4-5 years now. I've typically received a 50% discount through my distributor, and would imagine that any robotics team could/should receive the same. The 50% discount is actually cheaper than the discounted items on ebay (usually...)
I would certainly ask your distributer if you qualify for a discount, 'cause this stuff isn't cheap.
Overall, I've been extremely happy with their customer service, the quality of their product, and most importantly, the ease of using their product with our robot designs.
YMMV, best of luck!
BEN