Using last 30 days

Sale 1:

Sold for 6 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198308819102#!/compare/1521158400/1521244800

Buyer: https://backpack.tf/profiles/76561198799774016#!/compare/1521158400/1521244800

Confirmed, again, by bot.tf: https://i.imgur.com/tlwqWp0.png

X = 6.5

Sale 2:

Sold for 6 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198308819102#!/compare/1522454400/1522540800

Buyer: https://backpack.tf/profiles/76561198127654774#!/compare/1522454400/1522800000

Confirmed by bot.tf: https://i.imgur.com/tlwqWp0.png

X = 6.5

Sale 3:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198119149660#!/compare/1521072000/1521158400

Buyer: https://backpack.tf/profiles/76561198333349056#!/compare/1521072000/1521158400

X = 6

Sale 4:

Sold for 6 keys (ID’s match)

Seller: https://backpack.tf/profiles/76561198800248612#!/compare/1522368000/1522454400

Buyer: https://backpack.tf/profiles/76561198080202761#!/compare/1522368000/1522454400

X = 6

Sale 5:

Sold for 6 keys

Seller: https://backpack.tf/profiles/76561198198332539#!/compare/1521244800/1521331200

Buyer: https://backpack.tf/profiles/76561197997076098#!/compare/1521244800/1521331200

X = 6

Sale 6:

Sold for 5 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1521331200/1521417600

Buyer: https://backpack.tf/profiles/76561198314541844#!/compare/1521331200/1521417600

X = 5.5

Sale 7:

Bulk for Phosphorus Valley Forge

Seller: https://backpack.tf/profiles/76561198071478564#!/compare/1519948800/1520899200

Buyer: https://backpack.tf/profiles/76561198155420824#!/compare/1520726400/1520899200

Sale 8:

Sold for Midnight Whirlwind Buy a Life

Seller: https://backpack.tf/profiles/76561198079578383#!/compare/1520985600/1521244800

Buyer: https://backpack.tf/profiles/76561198396612584#!/compare/1521158400/1521244800

Can probably be used on the buy a life instead.

Sellers:

8 keys:

https://i.imgur.com/GzWbRUW.png

https://backpack.tf/item/6382952869

20 keys:

https://i.imgur.com/orzgiDq.png

https://backpack.tf/item/6294894809

http://www.tf2outpost.com/trade/29483088

Sales at:

5.5

6 (3x)

6.5 (2x)

SCM has buyers at almost 6 keys worth:

https://i.imgur.com/Kvm1eSd.png - excluding 5.5.

Going with 6-6.5.