I've got 4 pairs of Diesels that I've had for quite 5-6 years. Still a great fit, still feel great. I bought a pair last year that are excellent as well. They also do a "denim gallery" series made with some awfully nice japanese denim.
What is "low quality" denim, anyway? I mean, you can go get Wranglers from Target for 40 bucks and wear them day in and day out for the next 20 years, or you can do the same with jeans from APC, Helmut Lang, Dior, or whatever. Sure, there is _some_ variation in quality, but the simple fact is that the difference between your stock Wrangler or Lee jeans and basic Dior Homme jeans doesn't equate to the price difference. You are paying for the label, the exclusivity, the cut, and maybe some qualitative improvement in fabric that only a textile freak would notice, but you aren't really getting "better" denim. It's all cotton!
I'm guilty as charged when it comes to buying premium denim, and I feel like a bit of a fool for it, especially knowing that the differences are pretty goddamn minor.