Mini tubbing is a expensive decision. I think it's one of the key factors to the killer cars however. 7k that cheap to mini tub. Let me do a tally.
Wheels and tires: 5k
G Bar: 1600
Moser 2750
Labor:2500 minimum
Ricks tank or similar: 800
More like 11k-14k to do it like the top notch cars around here.
Oh ya and if you are going to spend that kind of money on a mini tub well the rest of the project has to be on the same level. Take your budget and double it and you are close. haha New guys are you listening.