Sale 1:

Sold for Searing Plasma Industrial Festivizer (23) + Haunted Ghosts Respectless Rubber Glove (23) Strange Pro. KS Rocket Launcher (11)

http://www.tf2outpost.com/trade/29275387 - No visible B/O, nothing cached

Seller: https://backpack.tf/profiles/76561198049149130#!/compare/1500508800/1500595200

Buyer: https://backpack.tf/profiles/76561198232702608#!/compare/1500508800/1500595200

X = 57

Sale 2:

Sold for 40 keys. Took, like, a year to sell - https://backpack.tf/item/2797713985

http://webcache.googleusercontent.com/search?q=cache:bQkNgNZY1JYJ:www.tf2outpost.com/trade/29262038+&cd=1&hl=en&ct=clnk&gl=au - B/O of 40

http://www.tf2outpost.com/trade/28904621 - B/O was 45 2 months prior to the sale

Seller: https://backpack.tf/profiles/76561198002757046#!/compare/1499904000/1499990400

Buyer: https://backpack.tf/profiles/76561198123596910#!/compare/1499644800/1499990400

Compare link shows that 57 keys match, but only 40 of them were involved. The other 17 came from selling the blizzardy honcho's.

X = 40

Sale 3:

Bulk for Duped Circling Heart Team Captain

Seller: https://backpack.tf/profiles/76561198028511217#!/compare/1496966400/1498176000

Buyer: https://backpack.tf/profiles/76561198080179568#!/compare/1496880000/1496966400

Sellers:

52 keys:

http://i.imgur.com/qV5RMmi.png - 3 days

53 keys:

http://i.imgur.com/iNvuZOf.png - 20 days

Sales at:

40

57

57 looks like an outlier, given the time it took to sell at 40, and the current sellers for cheaper. Excluding 57.

Going with 40 flat.