I've been wearing Levi's 501 since the early 80's and I have 8 pair of them from that time to around 1995 that are close to worn out by now (but soft, like pajamas almost). The quality of the denim between then and now is distinct.

For instance, I bought a pair 4 months ago (sadly, the last Levi's I'll ever buy) that ripped after getting caught on the corner of a desk. Any of the earlier pairs I have were put through much worse abuse (hunting in South Texas [thorny mesquite trees-dense brush], hiking/camping in New Mexico mountains, working in a truck repair shop) without any noticeable damage like a big rip.

The price has gone up even though they are clearly using lower quality denim. At ~$40 they're just not worth it. I never owned CK's or Jordache because Levi's looked just as good, were more durable and cost 50% less. Now, if I'm going to spend $40 for jeans, they might as well be CK's since those are clearly made of higher quality denim at least.

Levis aren't a good purchase anymore. Go with Dickies or Carhart for active use and anything but Levis for everyday wear.