most of that $ is in the cage I'd bet. I know I spent more on my 4x2x2 animal plastics cage than I did on my coastal.

As far as housing carpet pythons in tubs.. some people do it. I don't. Some coastals get big enough that they look cramped in 4x2x2s. Even as adults they can be fairly arboreal, if they are provided with stuff to climb on.