wow, most people won't come out and admit that. you can hear some weird things online, but i agree w/ mrcarcrazy, there's a lot of factors. i had a guy in last week w/ a truck that kept wearing tires out after 20k, and he couldn't understand why since he's on his third 20k set from discount shops that were supposedly doing alignments. well we put on new tires and aligned it properly, the knock out plugs were still in the slots of the control arms. meaning no one ever adjusted camber or caster, and it was way out.
so this guy spent over 600 bux every 20k for 60k. so thats almost 2,000 bux in tires and labor and if he keeps his alignment in spec these tires will last at least 60k costing him 600 instead of 2 grand.