I think a distinction needs to be made between parts & tools. Retrofitting new parts to old gear will always be a problem, even if it shouldn't be.
Tools are a different matter. StrewMac sells a lot of special purpose tools, which are always expensive. It helps to have access to good advice. My luthier scoffs at special purpose tools. E.g., Sometimes it's hard to get at a truss rod nut. Instead of buying an expensive dedicated wrench, he grinds down the diameter a standard socket wrench on the bench grinder.
Also, if you make or mod your own tools & jigs, you gain experience working with metal and wood, and power tools. This experience is applicable to working on more refined things like guitars and amp chassis.
@G. Hoffman: what size buffing wheel -- Dremel? Bench polisher? 8" 12"?
A lot of their special tools are a waste, but some of them are absolutely essential to some jobs. I would never try to make a nut without the gauged nut files they (and others) sell, not anymore. We used to do it, of course, but there is no way around the fact that a special tool does a better job in this case. Or the tool they make for fixing worn bridge plates, which does something you just can't do without it, and which is a very good fix for the problem - previously, we had to replace the bridge plate, which is about 5 times more expensive and has a significant effect on the value of the guitar. Tools like that aren't expensive, because they pay for themselves extremely quickly.
Then there are the tools which are really aimed at amateurs - things like the neck jig for fret work. Those things do the job intended reasonably well, and can make it easier for someone who doesn't know what they are doing, but waste a lot of time for anyone who wants to make a living (time is money, after all!)
Then there are the things which are just dumb, like the notched straight edge, or most of their dial indicator tools. Those do nothing particularly useful, and aren't really worth having.
The only parts I really buy from them, as I said, are dome knobs and some of their tuners (and yes, Waverly's really are worth the money - very nicely made). Their plastics are definitely not worth getting.
The buffer is just a basic bench top grinder, but we put a couple buffing wheels on them. It is important to get the stiffest buffing wheels you can get, though - it helps to keep the edges really clean. Hence the spiral stitched wheels. The current one is nice because it has an 1800 RPM motor, which keeps the heat down.
Gabriel