Sale 1

Buyer: https://backpack.tf/profiles/76561198095986590#!/compare/1514851200/1514937600

Seller: https://backpack.tf/profiles/76561198069206704#!/compare/1514764800/1514851200

Sale was at 9 keys. However, the trade was made in January, which was a trade that took place after the price suggestion 1 year ago. I'll leave it in for now.

Sale 2

Buyer: https://backpack.tf/profiles/76561198356370904#!/compare/1527638400/1527724800

Seller: https://backpack.tf/profiles/76561198204701269#!/compare/1525651200/1527724800

So the unusual hat was traded for 8 keys, 5 ref, and a Pink as Hell Straight Outta Sight. I personally don't value paint so I'm just going to leave it at the average of its price range, around 12.77 ref, which gives it a value of 8 keys and 17.77 ref, or 8.51 keys.

Sale 3

Buyer: https://backpack.tf/profiles/76561198204701269#!/compare/1525132800/1525651200

Seller: https://backpack.tf/profiles/76561198011321852#!/compare/1525392000/1525478400

For the seller, there is a lot of sales for them that day, but the buyer bought it for 10 keys pure.

Sale 4 (Optional?)

Buyer: https://backpack.tf/profiles/76561198210958265#!/compare/1525305600/1525392000

Seller: https://backpack.tf/profiles/76561198399778219#!/compare/1525305600/1531180800

Does selling to mannco.trade count? Let me know in the comments. Anyway the buyer bought the item from mannco.trade using his Vintage Cloak and Dagger Strange Professional Killstreak Bat, Aces High Big Elfin Deal, Strange Crit-a Cola), Genuine Tomb Readers, and a Strange Thrilling Track Suit. Taking the average of each of the item price ranges and adding it all together gives a value of 16.75 keys (!). I'm leaving it as optional for now, but let me know if I should include it or not in the comments.

So, (9 keys + 8.51 keys + 10 keys)/3 = 9.17 keys.

I'll leave the range at 9-9.5 keys for now.

EDIT: Just some formatting issues corrected.