Sale 1:

Sold for 7 keys + 24 ref

Seller: https://backpack.tf/profiles/76561198304138933#!/compare/1522886400/1522972800

Buyer: https://backpack.tf/profiles/76561198091428881#!/compare/1521072000/1522972800

Untraceable, but bot.tf confirms: https://i.imgur.com/dDg3udz.png

X = 8

Sale 2:

Sold for 7 keys + 25 ref

Seller: https://backpack.tf/profiles/76561198304138933#!/compare/1519776000/1519862400

Buyer: https://backpack.tf/profiles/76561198155558267#!/compare/1519689600/1519862400

Untraceable, but bot.tf confirms: https://i.imgur.com/dDg3udz.png

X = 8

Sale 3:

Sold to a bot for 7 keys + 24 ref

Seller: https://backpack.tf/profiles/76561198342161127#!/compare/1518566400/1518652800

Buyer: https://backpack.tf/profiles/76561198304138933#!/compare/1518566400/1518652800

Untraceable, bot.tf confirms: https://i.imgur.com/IoHZRdH.png

X = 8

Sale 4:

Sold for 8 keys

Seller: https://backpack.tf/profiles/76561198304138933#!/compare/1518998400/1519084800

Buyer: https://backpack.tf/profiles/76561198096779707#!/compare/1518998400/1519084800

Bot.tf confirms: https://i.imgur.com/dDg3udz.png

X = 8

Sales 5 & 6:

Sold for 8 keys + 4 ref

Seller: https://backpack.tf/profiles/76561198344933095#!/compare/1517616000/1517702400

Buyer: https://backpack.tf/profiles/76561198204218023#!/compare/1517616000/1517702400

Untraceable, but bot.tf confirms: https://i.imgur.com/dDg3udz.png

X = 8

In the same links, the buyer re-sold to the bot for 7 keys + 26 ref

X = 8, again

Sale 7:

Sold to a bot for 7 keys + 24 ref

Seller: https://backpack.tf/profiles/76561198107260155#!/compare/1519084800/1519171200

Buyer: https://backpack.tf/profiles/76561198304138933#!/compare/1519084800/1519171200

Bot.tf confirms: https://i.imgur.com/dDg3udz.png

X = 8

Sale 8:

Sold with more than 0.25 keys worth of ref for 8 keys

Seller: https://backpack.tf/profiles/76561198048851745#!/compare/1520380800/1520467200

Buyer: https://backpack.tf/profiles/76561198146112717#!/compare/1518825600/1520467200

X = 7.5

Sale 9:

Sold to a bot for 7 keys + 20 ref

Seller: https://backpack.tf/profiles/76561198050518375#!/compare/1522886400/1522972800

Buyer: https://backpack.tf/profiles/76561198304138933#!/compare/1522886400/1522972800

Bot.tf: https://i.imgur.com/dDg3udz.png

X = 7.5

Sale 10:

Bulk for some unusual sniper rifle

Seller: https://backpack.tf/profiles/76561198053717045#!/compare/1519948800/1520035200

Buyer: https://backpack.tf/profiles/76561198188268857#!/compare/1519516800/1520035200

Sale 11:

Bulk

Seller: https://backpack.tf/profiles/76561198112516663#!/compare/1519171200/1519257600

Buyer: https://backpack.tf/profiles/76561198053717045#!/compare/1519171200/1519257600

Sale 12:

Bulk for Purple Confetti Thirst Blood

Seller: https://backpack.tf/profiles/76561198188268857#!/compare/1520640000/1520726400

Buyer: https://backpack.tf/profiles/76561198073618741#!/compare/1520640000/1520726400

There are also 3 marketplace.tf sales that’ll end up being higher than the unsolds:

https://marketplace.tf/items/330;5;u31

Not comfortable using them here.

Sellers:

~7.7 keys:

https://i.imgur.com/O6IuZWZ.png

https://backpack.tf/item/1623479160

~7.75 keys:

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

https://backpack.tf/item/612663308

8 keys:

https://i.imgur.com/p7P7o26.png

https://backpack.tf/item/1098616939

~8.2 keys:

https://i.imgur.com/9ocRorT.png

https://backpack.tf/item/627337767

~8.7 keys:

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

https://backpack.tf/item/2361253058

Sales at:

7.5 (2x)

8 (7x)

Going with 7.5-8.