Wow you are right, not cheap.

I buy synthetic briefs either at chain stores (Target, Fred Meyer), or at discount stores (Filenes' Basement-when I was back East, and Marshalls/TJ-Max). Finding good synthetic briefs which fit well can be a challenge, but with some looking they can be found for $5/pair. I've found good synthetic briefs last much-much longer than cotton briefs do, but I don't wear cotton briefs for outdoorsy stuff.

I've had one set of 4 synthetic briefs for years now (maybe 5/6 years?). I've taken them on several tours (including my year tour), and a couple extended backpacks, as well as just using them day-to day. They are "Calvin Klein" brand which I bought on closeout at a Filene's Basement for like 15$ for the 4. They are black, but being synthetic I bleach them on occassion to "sterilize" them, and there is no problem with fabric degeneration.

I've probably thrown out 50$ or more worth of regular cotton briefs during the same time frame. The "Calvin's" are still pretty good, fit well, and have OK elastic. I've been looking for more of the same whenever I'm out shopping, but have never seen them again. I'm thinking the company might know that they made them too well and has discontinued them simply because they last so well.

Coolmax are allrite and I have a few pair, but the "Calvin's" I have are more of a mesh type nylon brief.