Maybe they can't pass a background!! Just checked eBay. Don't know enough about these to tell the difference between a fake. But it would appear the auctions are in the $3k-$10k price range.
I learned long ago to stay away from things I know nothing about and collectible shoes fall into that category.
Heck, I can hardly say it without laughing.
Screwy thing is they just re-issued the Air Mags, for around $69...
so unless they've got MJ Fox's autograph on 'em and were used in the movie...
$100 at best...