I totally get why you might not but for me, quality underwear has been a great purchase. They last longer, breath better, stay put, and synthetic ones are washable in a sink in a pinch when traveling(I mean they all are but these dry really quick)
I've found my expensive underwear to not last all that long, but to be amazingly more comfortable. There's no going back, especially when it's hot out.
My favorite is ExOfficio. I usually buy them when they're on sale because they can be highly variable in pricing. 15 to 30 dollars an item, for example, and usually not so cheap as 15. But the quality is great.
Edit: I used to use Patagonia, which are much better than standard underwear, but ExOfficio is better.