why do slickdealers like cheap headphones so much?
Because they don't already have a more expensive pair of headphones
Because they can't tell the difference
Because they are buying stuff for other people as gifts and have a budget
Because slickdealers upvote deals that are okay even if they don't make the purchase
Because cheap headphones have their uses, are less painful to replace, can be just for fashion.
That said, I think my px-100s have been worth every penny i paid ($42) for them, for versatily, portability and durability, even though I own RE-0s and have tried other more expensive headphones (that I couldn't imagine owning any time soon).
Audiophiles have their own forum; slickdealers belong here.