It can vary depending on what you go with. A motor with rods, modified pistons, cam, injectors, studs and machine work/balancing will run you about 13 - 15 k. Twin cp3's, Turbo, EFIlive, lift pumps, and all the other stuff to make it work right will be another 10 or so. This would assume you do your own assembly/install work.
I'm sure you could make 700 hp for less money, but I don't know how well it would hold together. Starting from scratch, you could build the motor for 23-25k with all the goodies. I don't think I'm too far off on the numbers. The tranny/converter, exhaust,e-locker, traction bars, guages front end upgrades will run another 8k.
30+k
will get you a pretty good set-up.