When looking for parts it may be possible to mention membership of an enthusiast club - the United States Lexus Owners' Club, for examp;e - and ask if the vendor or sellor is willing to give a discount in exchange for positive feedback in a forum such as this. Perhaps some Lexus dealers would be interested in this type of feedback. That was the intention of the thread mentioning the discount. Not sure why that link is dead but I'll check it out.
Anytime aftermarket brands are considered, quality needs to be accounted for. Things like pcv valves are usaully pretty simple devices and aftermarket pieces are just fine. Always ask about a warranty on aftermarket items - like starters and the like.
There are ways to get around high cost parts. The distributor cap for example, may be sourced from toyota a little cheaper (who knows) - I haven't yet tried. But the 93 to 97 supra na has the same motor. NAPA or other car parts chains may be able to cross reference a suitable aftermarket piece. Call them and tell them what you are looking for with vehicle and engine info - ie 6 cylinder SC300. They probably can offer a cap, plugs and wires cheaper.
I don't know the manufacturers of those items off hand. Typical toyota suppliers are Nippon Denso, Sumitomo, NTK and millions more.
There is always the potential for a deal. I often check for used or off hand parts in classified forums and in salvage yards like www.taprecyling.com, or ebay.
That's all I've really got for now. Keep looking - let us know of any great deals or good sites. At 17% off, the site linked sounds pretty good. Let us know how it works out. I'll see what else we can dig up.
Good luck. Keep surfing.