Sale 1:

Sold for Max’s Head (~19 at the time) + ~3 keys in pure/items

Seller: https://backpack.tf/profiles/76561198339104273#!/compare/1512864000/1512950400

Buyer: https://backpack.tf/profiles/76561198156032540#!/compare/1512864000/1512950400

X = 22

Sale 2:

Sold for Bubbling Backwards Ballcap (Suggestion at 14) + 7 keys

No outpost

Seller: https://backpack.tf/profiles/76561198346118738#!/compare/1512086400/1512172800

Buyer: https://backpack.tf/profiles/76561198161635287#!/compare/1512000000/1512172800

X = 21

Sale 3:

Sold with ~5 keys in items for Stormy Towering Pillar of Hats (21.5)

http://www.tf2outpost.com/trade/29475400 - B/O of 27

Seller: https://backpack.tf/profiles/76561198156032540#!/compare/1512864000/1512950400

Buyer: https://backpack.tf/profiles/76561198134266699#!/compare/1512864000/1512950400

X = 17

Sale 4:

Something involving a Circling Heart Coupe

Seller: https://backpack.tf/profiles/76561198148733839#!/compare/1511308800/1511395200

Buyer: https://backpack.tf/profiles/76561198346118738#!/compare/1511308800/1511395200

No current sellers.

Bubbling Ballcap:

https://backpack.tf/suggestion/5a76c45ecf6c757a8e15ac79

Sales at:

17

21

22

17-22.