User blog comment:Kentnar/How to be an actual god at trading?/@comment-32197189-20190901104700/@comment-32197189-20190903014035

Short answer: I don't know.

I would suspect it's due to the fact that at the time, beta tails were the only good tail items, and party hats were very noticable. Head items tend to be better than leg items, because they're a more noticable flex.

Den items can't be flexed, so that's what tends to devalue them.

Bubbletrons are underwater, which means you needed to go underwater to flex them.