I think y'all may be shooting low with a $5k estimate. If you purely base the cost on the supercharger and intercooler, your looking at 2,800 and about 1,000 respectively. Plus brackets, piping and accessories and profit I would say 5,999-6,500 would be fair. Don't forget about fuel and engine management either...
A company by URD makes an identical setup for the 1GR, the Toyota Tacoma, 4Runner and FJ Cruiser motor which is a 4.0L running the C38 and runs about 5,899. It does double the wheel hp from 200ish to 400ish which gives me a promising expectation from this kit.
Underdog Racing Development
Just a wild guess
Nick J.