I buy pants from Costco but they always wear out after 2 years with big holes in the seat. Where do you even buy something that lasts 10 years?
Wearing longer boxer shorts can lessen it, but the best thing is to find pants with a roomier fits, ie. old-fashioned straigh-legged jeans or chinos with pleats, that sort of thing. The looser fit lets the fabric move around, instead of rubbing in the same places all the time.
I've been very happy with reproduction Bundeswehr "moleskin" pants in black, they're like the dressy version of cargo pants, made from thick cotton fabric. You can take out the threads that hold the cargo pockets on, and then you have a comfortable and durable set of pants that don't look like you're some kind of security guard.
I don't know if you can get them in the states, they're widely available in Europe.
Otherwise look for slightly-old-fashioned menswear in thick cotton or wool fabrics. Good Tweed lasts for decades, if you don't mind the style. Don't go to big box stores, look for the dedicated niche menswear stores.