From the auction:
"This is perhaps the most famous Mountain Dew bottle in America."
Yep. Meaning that about 5 people care of it and maybe a few dozen have heard of it, as opposed to the zero and 1 figures for the average Mountain Dew bottle.
Assuiming it's even real, to want to pay $12 for that bottle, you'd have to either be stuipd enough to believe that it'll be worth something in a few years (when nobody will care, or even remember this promotion), or that they really, really want that Mountain Dew error because it means something to them personally.
If they're in the former category, they're idiots. If the latter... uh... glad they're not me, anyway.
Hey, I once found a box of mint chocolate chip ice cream with one giant chocolate chip in the middle (chip machine must've jammed), and a can of pork and beans with screws in it... should've eBayed them! I could've made millions!