Welp, researched this and then I saw that a suggestion was already made using the same sale but was closed for some reason. I'm sure this is still usable though. 1 ez pure sale

Halloween 2014 + Robo Hat :D

http://forums.backpack.tf/index.php?/topic/43611-a-rather-unusual-price-suggesting-game/

Sale 1

Sold for 21 Keys Pure

Seller's BP

http://backpack.tf/profiles/76561198085540473?time=1436684400

http://backpack.tf/profiles/76561198085540473?time=1436770800

http://backpack.tf/profiles/76561198085540473?time=1436684400&compare=1436770800

Buyer's BP

http://backpack.tf/profiles/76561198225485028?time=1436684400

http://backpack.tf/profiles/76561198225485028?time=1436770800

http://backpack.tf/profiles/76561198225485028?time=1436684400&compare=1436770800

Fruit Shoot was bought off marketplace.tf as well as the keys

http://www.tf2outpost.com/trade/26441109 - Buyer offered 21

Key histories match

= 21 Keys

Sale 2

http://backpack.tf/vote/id/55cfef86ba8d881e7d8b4575

Used to price Frostbite War Pig, also not usable due to being such a small part of the trade

Not usable

Seller at 39 Keys: http://www.tf2outpost.com/trade/27080555

One recent sale at 21 Keys, taking a flat range at 21 Keys