Sale 1:

Sold for 6 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198308819102#!/compare/1522713600/1522800000

Buyer: https://backpack.tf/profiles/76561198388363768#!/compare/1522713600/1522800000

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

X = 6.5

Sale 2:

Bought for 6 keys + 1 ref, according to bot.tf

Seller: https://backpack.tf/profiles/76561198144919311#!/compare/1522022400/1522281600

Buyer: https://backpack.tf/profiles/76561198308819102#!/compare/1522195200/1522281600

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

X = 6

Sale 3:

Sold to a quickbuyer for 6 keys

Seller: https://backpack.tf/profiles/76561198415535845#!/compare/1520899200/1520985600

Buyer: https://backpack.tf/profiles/76561198048851745#!/compare/1520899200/1520985600

X = 6

Sale 4:

Bought, again, for 6 keys + 1 ref, according to bot.tf

Seller: https://backpack.tf/profiles/76561198085998464#!/compare/1522713600/1522800000

Buyer: https://backpack.tf/profiles/76561198308819102#!/compare/1522713600/1522800000

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

X = 6

Sale 5:

Sold for 5 keys

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1522368000/1522454400

Buyer: https://backpack.tf/profiles/76561198085998464#!/compare/1522454400/1522713600

X = 5

Sellers:

~6.7 keys:

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

https://backpack.tf/item/3146953527

7 keys:

https://i.imgur.com/8Eagbmh.png

https://backpack.tf/item/5055871245

https://i.imgur.com/sIB7o1K.png

https://backpack.tf/item/4263889319

https://i.imgur.com/30xOMID.png

https://backpack.tf/item/2819420791

29 keys:

https://i.imgur.com/3GQ7D68.png

https://backpack.tf/item/2776236643

Sales at:

5

6 (3x)

6.5

The sales at 6, despite going to quickbuyers, are far too common to be excluded. Keeping 6 in the range.

https://i.imgur.com/CFtjEt3.png - SCM buyers at ~5, excluding 5.

Going with 6-6.5.