How much it's going to cost will depend on how much of it you do yourself. Assuming that you have the truck, you can do a Mamba Max esc for 4S lipo (with the internal bec disabled) ~$129, a Feigao 8XL motor ~$80, radio ~$175 for a nice one, bec for ~$10-$40, and anything else that you don't fabricate yourself. As for the batteries, the $250 you've allocated might get you a charger and A battery, but don't forget the balancer for ~$40.

All I can tell you is to avoid throwing it together. Take your time and make sure it's done right; otherwise you're in for a lot of headaches.