For $100 you could build your own chamber easily, and probably get a good deal more space out of it. You should shop around before you drop a big wad of cash at the aquarium shop. It's nice getting new stuff but things from pet stores are almost universally overpriced. I get my terrariums from the guy who runs the place where I used to buy chinchilla chow when I lived back home - he gives used ones to me for free, and told me he usually throws them in the recycling if there's an excess, like when they get new holding tanks for the fish section, because it's a bother to clean the blackout paint and backing off. He usually has two or three handy every six months or so, usually 20- or 29-gallon tanks because they don't usually use anything bigger in the shop. You can get a 50-gallon tank for much cheaper than $100 if you look around - maybe try the classifieds on craigslist.