Diesel Jeans are great! the only ones i wear, pretty expensive though! but they sit&fit perfect!
replica diesel/replica jeans in general SUCK bigtime, not comparable to genuine diesel jeans! you get what you pay for.
the color will fade, the buttons will break (because they are made differently, diesel buttons are almost impossible to break), you'll be disappointed after a while!
as for the price, those diesel jeans cost the same almost everywhere! even in 3rd world countries you pay 200$ for a pair of genuine ones. the older models are usualy cheaper... i once got a pair which was 4 years old for 60$ at an end-of-season sale