Your seller is never bumped and sold all 3 collectors to 1 guy. It appears as a quicksale.

However, with all these solds, why not start with 5 keys. Upvote.

p.s. to support your suggestion:

http://www.tf2outpost.com/trade/18928423 - a buyer @ 3 keys. He's looking for chemistry set of collector's soda popper. It costs to craft it around ~1.5 keys, which makes it 4.5 keys in total

While the soda popper definitely is not worth 2 buds, 5 keys seems quicksellish especially as collectors go. Maybe give it a little more time

Selling for ridiculously high prices doesn't mean they sell for ridiculously high prices.

Just to make things clear - last link seller hasn't sold for 1 bud it lol.

http://www.tf2outpost.com/trade/18952746 - he just closed that trade

Also, it's pretty fine when people set such b/os on collector's items. The only problem that they don't sell for that much.