They are in the neighborhood of $200-$300, but you should check on the website to see. FYI - I've always had good luck reaching them by phone with questions. Great people to deal with!
I believe the bag comes with a bunch of palm-sized paper packets of desiccant, but that you can order a much more convenient canister (about 6" diameter, 2+ feet long) separately. They can both be re-used indefinitely by going through an easy oven-baking process, just before you're ready to put them into use. The packets are cut open and dumped into your own tray for baking and re-use (you then use the tray full of it under your car), but the canister can just be placed into the oven (your kitchen oven and no it won't smoke up the house or make a mess), baked, and then wrapped in aluminum foil to keep it sealed before you're ready to use it. You need it put it into use very soon after baking through. CarBag provides all this information in detail.
I actually use both a tray full of the desiccant and a canister, as you can never have too much!