Sale 1:

Sold for Peace Sign Prancer’s Pride (Suggestion at 12.5) + ~1.5 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561198274139380#!/compare/1507334400/1507420800

Buyer: https://backpack.tf/profiles/76561198262989290#!/compare/1507334400/1507420800

X = 14

Sales 2 & 3:

Sold for $22.88 and $28.58 on Marketplace.tf

https://marketplace.tf/items/174;5;u35

22.88/2 = ~11.4

28.58/2 = ~14.3

X = 11 and 14

Sale 4:

Sold for 10 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198387946447#!/compare/1512259200/1512345600

Buyer: https://backpack.tf/profiles/76561198090602679#!/compare/1512259200/1512345600

X = 11

Sale 5:

Sold for 11 keys + some ref

Seller: https://backpack.tf/profiles/76561198090602679#!/compare/1512259200/1512345600

Buyer: https://backpack.tf/profiles/76561198137056305#!/compare/1512259200/1512345600

X = 11

Sale 6:

Sold for 10 keys to a quickbuyer

Seller: https://backpack.tf/profiles/76561198295263968#!/compare/1508803200/1508889600

Buyer: https://backpack.tf/profiles/76561198153806405#!/compare/1508803200/1508889600

X = 10

Sale 7:

Sold for 10 keys in ~1 day

Seller: https://backpack.tf/profiles/76561198267189538#!/compare/1508630400/1508716800

Buyer: https://backpack.tf/profiles/76561198119345892#!/compare/1508630400/1508716800

X = 10

Sale 8:

Most likely sold for 10 keys + 4 ref (Buyer’s compare link)

Seller: https://backpack.tf/profiles/76561198119345892#!/compare/1508716800/1508803200

Buyer: https://backpack.tf/profiles/76561198323349846#!/compare/1508716800/1508889600

X = 10

Sale 9:

Sold with Spec. KS Minimal Wear Sand Cannon for Green Energy Hard Counter

Seller: https://backpack.tf/profiles/76561198262989290#!/compare/1507334400/1507420800

Buyer: https://backpack.tf/profiles/76561198219836673#!/compare/1507334400/1507420800

https://backpack.tf/item/882961049 - Whoopee

https://backpack.tf/item/180472909 - Counter

Should be used on the Counter.

Sale 10:

Sold with some ref for Cloud 9 Counterfeit Billycock

Seller: https://backpack.tf/profiles/76561198153806405#!/compare/1509840000/1509926400

Buyer: https://backpack.tf/profiles/76561198282902145#!/compare/1509753600/1509926400

Can be used on the billycock.

Sale 11:

Sold for Strange Pro. KS Grenade Launcher (~7.5) + 3 keys and most likely something else

http://www.tf2outpost.com/trade/29430428 - B/O of 13

Seller: https://backpack.tf/profiles/76561198282902145#!/compare/1510099200/1510185600

Buyer: https://backpack.tf/profiles/76561198073168400#!/compare/1510185600/1510272000

Seller’s end shows something sold for a key and some ref, but I couldn’t find anything else in the buyer’s end that went to the seller. Will exclude this sale due to uncertainty

Sale 12:

Weird bulk sale

Seller: https://backpack.tf/profiles/76561198073168400#!/compare/1510444800/1511395200

Buyer: https://backpack.tf/profiles/76561198014273034#!/compare/1511395200/1511481600

Sellers:

11 keys:

https://i.imgur.com/qshMVpD.png - 3 days

12 keys:

https://i.imgur.com/ptgTAfB.png - 7 days

14 keys:

http://www.tf2outpost.com/trade/29387844 - 2 months

Sales at:

10 (3x)

11 (3x)

14 (2x)

14 looks like an outlier with the cheaper sellers and the 2-month unsold at 14. Excluding 14.

10 quicksold and went to quickbuyers. Excluding 10.

Going with 11 flat.