I think that the denim jeans found on the high street are just as resilient as designer denim. However, the high street brand may not be available in all shapes & sizes. They tend to only cater to the masses where you will find that the designer label has a much wider range of sizes, leg lengths (full leg, Capri etc.) & styles (straight, bootleg etc.).
As all denim is basically cotton woven in the same way, I believe that in many cases you are just paying extra for the social status for a designer label.
Many people that I know wear cheaper jeans to work, especially if it is to a manual labour job. These jeans would stand up to a lot of hardship & while they tend to get very dirty they also stand the test of time & remain intact.
I think that we need to consider that in many cases it has more to do with value the manufacturer places on the jeans than the quality of the denim itself. High street retailers do not heavily advertise their jeans where as the designer labels do. I think that it is this extra advertising & branding that puts a large price tag on a lot of designer denim.
