I ordered it direct, but its been a few month ago. Others have ordered from Amazon, I think the price is the same..
It should last you quite a while, if you spot clean really well, meaning not leaving any soiled substrate behind, you almost never have to do a complete clean out.
I usually have it around 1/2 inch thick or so, but the snakes push it around sometimes, esp. when it is very dry and fluffy. So sometimes they push it towards the side and it can get deeper there while they lay on the bottom, LOL. Next day it seems to be pushed back..
You don't need it really deep, though, but about 1/2 inch or so I'd say. This way it will soak up any mess nicely.