0-30 days:

Sale 1:

Sold for Steaming Steel Toe (Mini at 8 below) + 2 keys

No outpost

Seller: https://backpack.tf/profiles/76561198004695107#!/compare/1515715200/1515801600

Buyer: https://backpack.tf/profiles/76561198358646453#!/compare/1515715200/1515801600

X = 10

Sale 2:

Quicksold for 10 keys

Seller: https://backpack.tf/profiles/76561198143969056#!/compare/1515888000/1515974400

Buyer: https://backpack.tf/profiles/76561198204249201#!/compare/1515801600/1515888000

X = 10

Sale 3:

Sold for 9 keys

Seller: https://backpack.tf/profiles/76561198281580442#!/compare/1515628800/1515801600

Buyer: https://backpack.tf/profiles/76561198004695107#!/compare/1515715200/1515801600

X = 9

Sale 4:

Sold for ~8 keys in items

Seller: https://backpack.tf/profiles/76561198314725749#!/compare/1515974400/1516233600

buyer: https://backpack.tf/profiles/76561198158937070#!/compare/1516147200/1516233600

X = 8

Sale 5:

Bulk for Scorching Noh Mercy

Seller: https://backpack.tf/profiles/76561198112099979#!/compare/1513555200/1513728000

Buyer: https://backpack.tf/profiles/76561198085628805#!/compare/1513641600/1513728000

Sale 6:

Quicksold for some amount of keys

Seller: https://backpack.tf/profiles/76561198204249201#!/compare/1515888000/1515974400

Buyer: https://backpack.tf/profiles/76561198314725749#!/compare/1515456000/1515974400

30-60 days:

Sales 7 & 8:

Sold for $28 and $35 on Marketplace.tf

https://marketplace.tf/items/30614;5;u3015

https://backpack.tf/item/5256439363 (can’t identify the other one’s history)

35/1.96 = ~17.9

28/1.9 = ~14.7

X = 15 & 18

Steaming Steel Toe Mini:

Sale 1:

Sold for 8 keys + 10 ref after ~3 months

Seller: https://backpack.tf/profiles/76561198344933095#!/compare/1515628800/1515715200

Buyer: https://backpack.tf/profiles/76561198267717108#!/compare/1515715200/1515801600

X = 8

Sale 2:

Sold for 8 keys + ~15 ref worth of items

Seller: https://backpack.tf/profiles/76561198023542389#!/compare/1515715200/1515801600

Buyer: https://backpack.tf/profiles/76561198104925026#!/compare/1515715200/1515801600

X = 8

Sale 3:

Sold for 8 keys + 8 ref

Seller: https://backpack.tf/profiles/76561198304138933#!/compare/1513900800/1513987200

Buyer: https://backpack.tf/profiles/76561198067053408#!/compare/1513814400/1513987200

Ref appears on the seller’s end, keys appear on the buyer’s end.

X = 8

Sale 4:

Sold for 8 keys + 8 ref

Seller: https://backpack.tf/profiles/76561198049149130#!/compare/1515974400/1516060800

Buyer: https://backpack.tf/profiles/76561198097502657#!/compare/1515974400/1516060800

X = 8

Sellers:

12 keys:

https://i.imgur.com/cOsJZJF.png - 13 days

14 keys:

https://i.imgur.com/x0v4exJ.png - 10 days

Sales at:

8

9

10 (2x)

15

18

Sales at 15 and 18 occurred more than 30 days ago, and should be excluded. The cheaper sellers support this.

8 looks low, excluding 8.

Going with 9-10.