Using last month

Sale 1:

Sold for 17 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198316249813#!/compare/1522195200/1522368000

Buyer: https://backpack.tf/profiles/76561198106826389#!/compare/1522281600/1522368000

X = 17

Sale 2:

Sold for $12 on Marketplace.tf

https://marketplace.tf/items/1113;5;u3008

Can’t find item’s history

12/1.98 = ~6.06

X = 6

Sale 3:

Sold for 5 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198348237813#!/compare/1524268800/1524528000

Buyer: https://backpack.tf/profiles/76561198200654130#!/compare/1524096000/1524268800

X = 5

Sellers:

8 keys:

https://i.imgur.com/AICc2op.png

https://backpack.tf/item/2936344777

~8.65 keys:

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

https://backpack.tf/item/3287156543

15 keys:

https://i.imgur.com/I6LeYVO.png

https://backpack.tf/item/6451373924

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

https://backpack.tf/item/3286462705

21 keys:

https://i.imgur.com/vtKqsH3.png

https://backpack.tf/item/6396523994

28 keys:

https://i.imgur.com/1igaTlW.png

https://backpack.tf/item/2761594087

SCM: (Taking keys as $2.47)

https://i.imgur.com/jLkfgNL.png (only the first 3 matter here)

$17.10 (~6.92 keys)

$17.14 (~6.94 keys)

$18.68 (~7.56 keys)

Sales at:

5

6

17

17 is a large outlier, excluding.

https://i.imgur.com/OtHPsFf.png - Buyers at 5+ keys, excluding 5.

Going with 6 flat.