Maybe he has to save some more.
Plywood/concrete block tanks are cheaper compared to different materials but they can still get expensive. I have put 1500 in mine so far, and still have more to spend before I fill it. I did use some of the more expensive materials... fiberglass, west system, and tempered glass.
The filtration portion is going to run me about 800 for the pumps, plumbing, and filters.