Coroplast What is the best place to get Coro?

I've looked on this website's coro page and is their coro a good deal? If my math's right, it's roughly 10 sq ft per piece and 5 pieces for $20?? (29 inch X48 inch per sheet, you get 5 for $20) Is this a good deal? Maybe my math is just wrong, but it seems like a good deal. If not, where are some good places to get it, preferably where I can order online and ship to either home or store?