Jeans are a complicated story :S - the best made and most comfortable ones I've got are actually Crosshatch 55s but I'm a little bit of a brand snob and generally wear Levis but even Levis are a story of their own - depending on where they are made you get HUGELY different quality and the ones made in some factories are pretty much no different to any random £15-20 pair :S - IIRC the ones made ("authentic") in China, Bangladesh or Colombia have half the material thickness and lower quality fastenings, etc. whereas the ones made in Portugal, Turkey, United States, Japan or Italy are closer to the original quality - still not as well made as they used to be though.
Got a few different brands including Armanis, etc. and there are very few real designer jeans that aren't just a bit of cheap material with a brand name and corresponding price slapped on it sadly