Using last month.

Sale 1:

Sold for $55 on Marketplace.tf

https://marketplace.tf/items/463;5;u3010

55/1.97 = ~27.9

X = 28

Sale 2:

Sold for 15 keys

Seller: https://backpack.tf/profiles/76561198334598690#!/compare/1525392000/1525478400

Buyer: https://backpack.tf/profiles/76561198118680505#!/compare/1525392000/1525564800

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

X = 15

Sale 3:

Sold for 13 keys in a raffle

Seller: https://backpack.tf/profiles/76561198013011182#!/compare/1524182400/1524268800

Buyer: https://backpack.tf/profiles/76561198177665462#!/compare/1524268800/1524355200

X = 13

Sale 4:

Sold for 10 keys + 2.11 ref in a raffle

Seller: https://backpack.tf/profiles/76561198088250438#!/compare/1523923200/1524441600

Buyer: https://backpack.tf/profiles/76561198013011182#!/compare/1524009600/1524096000

X = 10

Sale 5:

Sold with ~0.5 keys in ref for Holy Grail Shred Alert

Seller: https://backpack.tf/profiles/76561198011321852#!/compare/1525392000/1525478400

Buyer: https://backpack.tf/profiles/76561198057999351#!/compare/1525392000/1525478400

Can be used on the Shred.

Sale 6:

Sold for SGG Square Dance + ~24 keys in pure/items

Seller: https://backpack.tf/profiles/76561198044794036#!/compare/1525046400/1525132800

Buyer: https://backpack.tf/profiles/76561198053151125#!/compare/1525046400/1525219200

phat outlier, excluding.

Sale 7:

Bulk for Beams Chill Chullo

Seller: https://backpack.tf/profiles/76561198115062041#!/compare/1525392000/1525478400

Buyer: https://backpack.tf/profiles/76561198071890767#!/compare/1524787200/1525478400

Sellers:

~14.6 keys:

https://i.imgur.com/65d0jRw.png

https://backpack.tf/item/2235962775

15 keys:

https://i.imgur.com/cFq6A2o.png

https://backpack.tf/item/5274720569

18 keys?:

http://www.tf2outpost.com/trade/29630756

89 keys:

https://i.imgur.com/F764K9i.png

https://backpack.tf/item/5288441771

Offers:

http://www.tf2outpost.com/trade/29436856

http://www.tf2outpost.com/trade/29609378

Sales at:

10

13

15

28

https://i.imgur.com/7bRuUXk.png - Buyer at 10 (will probably be gone when they see the suggestion), 10 seems low anyways. Excluding 10.

28 is an outlier, excluding.

13 may have sold in a scrap.tf auction, which usually gets excluded if the sale seems low, but given the next highest sale is currently higher than sellers, it should be fine to include 13 in the range here.

Going with 13-15.