Given all the other options out there, primarily the Holley, I wouldn't pay more than $1,000 for ANY BS3 system.
Upgrades are costly, the boxes are too specific to particular engine platforms, and the resale value is in the tank. Functional, but archaic Atari like software.
I've had both, and would pay twice the price for a Holley than a Big Stuff. The self learning feature also helps get the tune in shape quickly!
If your tuner ONLY works with Big Stuff, that's one thing, but if you tune yourself or the tuner knows Holley systems, keep shopping.
Good luck with it.
If an individual is going to tune the motor himself then from the little bit I have worked with the Holley unit I would agree.
But if he is going to hire a tuner go with whatever he likes and also consider what the other locals are using.