The price of coroplast depends on your area. It can be as much as $50.00 for a 4'x8' sheet (which is the size you want). Just look in your phone book and start calling. Okay, if you just get one box of grids I'm sure you can make a 2x3 or 2x4 (2x4 is the bare minimum for 2 cavy's which is what you should get, 2 piggys, if you get a boar you need to make it bigger) cage and a stand, and for that you would only need one sheet of coroplast, plus the toys and bowls and water bottles, and all that good stuff
and the bedding or fleece. So it really depends on what you get and where you get it.