I like Jumping

Drop the base

Sales:

https://steamcommunity.com/market/listings/440/Collector%27s%20B.A.S.E.%20Jumper

One sale at ~38 Keys (Rounding to the nearest Key for neatness) and the other is ~25 Keys <-- Seems low compared to other sales

https://marketplace.tf/items/1101;14 - Sold for ~53 "Keys" <-- Seems a little high, too sharp of an increase and the sale is slightly on the old side (2 Months old)

Only seller is @ 80 Keys

Buyers Buy @ 20 Keys Unsuccessfully

https://backpack.tf/profiles/76561198044684270#!/compare/1536192000/1537315200

Credits to DedAndrei for starting a suggestion

Thanks =)