Will be excluding non-pure and marketplace.tf sales, as pure sales are pretty abundant here.

Sale 1:

Sold for 11 keys (Buyer’s compare link)

Seller: https://backpack.tf/profiles/76561198125791160#!/compare/1510617600/1510704000

Buyer: https://backpack.tf/profiles/76561198193262358#!/compare/1510704000/1511740800

X = 11

Sale 2:

Sold for Aussie FaN (~10 at the time)

No outpost

Seller: https://backpack.tf/profiles/76561198314160142#!/compare/1508025600/1508112000

Buyer: https://backpack.tf/profiles/76561198297818905#!/compare/1508025600/1508112000

X = 10

Sale 3:

Sold for 10 keys + some ref (ID’s match)

Seller: https://backpack.tf/profiles/76561198143419353#!/compare/1510444800/1510617600

Buyer: https://backpack.tf/profiles/76561198079405234#!/compare/1510617600/1511049600 (best link available, doesn’t show purchase)

X = 10

Sale 4:

Sold for 10 keys

Seller: https://backpack.tf/profiles/76561198382654640#!/compare/1509753600/1509840000

Buyer: https://backpack.tf/profiles/76561198120000460#!/compare/1509753600/1509840000

X = 10

Sale 5:

Sold for ~9 keys + 21 ref to a bot

Seller: https://backpack.tf/profiles/76561198227232564#!/compare/1511481600/1511568000

Buyer: https://backpack.tf/profiles/76561198382654640#!/compare/1511481600/1511568000

X = 10

Sale 6:

Sold for 8 keys + ~1.6 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561198267189538#!/compare/1509840000/1509926400

Buyer: https://backpack.tf/profiles/76561198111607444#!/compare/1509408000/1509926400

X = 10

Sale 7:

Most likely sold for 10 keys

Seller: https://backpack.tf/profiles/76561198126979379#!/compare/1510876800/1510963200

Buyer: https://backpack.tf/profiles/76561198355667121#!/compare/1510876800/1511049600

X = 10

Sale 8:

Sold for 9 keys + at least half a key in metal

Seller: https://backpack.tf/profiles/76561198382654640#!/compare/1512172800/1512259200

Buyer: https://backpack.tf/profiles/76561198172820673#!/compare/1512172800/1512259200

X = 10

Sale 9:

Sold to a quickbuyer for 9 keys

Seller: https://backpack.tf/profiles/76561198171858153#!/compare/1511308800/1511395200

Buyer: https://backpack.tf/profiles/76561198045466865#!/compare/1511308800/1511395200

X = 9

Sale 10:

Sold for ~9 keys to a bot

https://i.imgur.com/DmT1yBs.png - Bot’s Buy-order

Seller: https://backpack.tf/profiles/76561198179654479#!/compare/1512086400/1512172800

Buyer: https://backpack.tf/profiles/76561198327061935#!/compare/1512086400/1512172800

X = 9

Sale 11:

Sold to a quickbuyer for 9 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198112516663#!/compare/1509840000/1509926400

Buyer: https://backpack.tf/profiles/76561197963500354#!/compare/1509840000/1509926400

X = 9

Sale 12:

Sold for 9 keys + 7 ref to a bot

Seller: https://backpack.tf/profiles/76561198326321981#!/compare/1511740800/1512172800

Buyer: https://backpack.tf/profiles/76561198026129220#!/compare/1512086400/1512172800

X = 9

Sale 13:

Sold with ~1.5 keys worth for Kill-a-Watt Sola Topi

Seller: https://backpack.tf/profiles/76561198312489081#!/compare/1510704000/1510876800

Buyer: https://backpack.tf/profiles/76561198126979379#!/compare/1510617600/1510704000

To be used on the Sola.

Sellers:

~9.9 keys:

https://i.imgur.com/eKysl8F.png - 1 day

10 keys:

https://i.imgur.com/zY5XbXI.png - 5x

https://i.imgur.com/kJ8kbCI.png - 2 days

~11.6 keys:

https://i.imgur.com/6CZLi7R.png - young

12 keys:

https://i.imgur.com/EBgdBUE.png - 11 days

Sales at:

9 (4x)

10 (7x)

11

Sells to quickbuyers for 9 pretty often. Keeping 9 in the range.

Excluding 11, given the amount of sellers for 10, and the lack of other sales at 11.

Going with 9-10.