Bart, just because someone has a different opinion than yours or a different desire does not make it wrong.
Yes, cheap underdash options exist but that is not what he wants.
The number of parts is no different between a hand selected system and the "kit" from Vintage Air or Old Air products. Sure, you have to order from a "dizzying" 3 places instead of 1. Is that worth saving $400? Up to you.
I don't know if you have actually built one of their kits, but they come with a selection of parts to pick from as you go. None of the off the shelf kits I have personally built ended up having all the pieces I needed to make a clean installation, resulting in needing to go out and find compatible parts halfway through the project to finish it. It is much easier to make a plan up front and buy the right parts the first time.
This is not at all like a wiring harness where you can just buy one off the shelf and it drops in. The selection of fittings is very specific to your particular installation. Unlike building a wiring harness from scratch, there are no minimum orders for supplies and no additional fabrication work.
Even if you buy the all in one kit, you still have to do the same amount of hose routing, cutting, crimping, assembly, etc. The one thing a kit gets you is a single point of contact to call with questions.
