I agree that the prices appear reasonable, but on the high side of what I'd consider a range of possible costs.

I went the SLR route and bought the following:
- 26.5 Torsion bars: $195
- Stage suspension setup: $695 (I already had some of the parts)
- SLR Steering $708

I already had, installed in the last year:
- 20% stiffer Bilsteins (5100), $240
- SLR 2" Shackle $50
- Idler arm brace: $60

So, it's not a cheap upgrade, but in my opinion, it's worth it. The torsion bars are a must, as is the steering. When I looked at the stock setup vs the SLR product, there was no comparison and I felt the difference immediately.

I also agree that this is something that you and someone else could do yourself. While your quote is only $375 for the install (which seems low), doing this work will help you to understand how the pieces go together so that you can crawl under your truck in the future and not have to pay someone for something that you and a wrench can do pretty easily.