Sale 1:

Sold for Kill-a-Watt Herald’s Helm (Suggestion at 17)

Seller: https://backpack.tf/profiles/76561198882972479#!/compare/1551571200/1551744000

Buyer: https://backpack.tf/profiles/76561198317790700#!/compare/1551657600/1551744000

https://backpack.tf/item/7414252657

https://bot.tf/stats/listings/YD72XVK4 - B/O of 25

X = 17

Sale 2:

Sold for 14 keys

Seller: https://backpack.tf/profiles/76561198095943714#!/compare/1551312000/1551571200

Buyer: https://backpack.tf/profiles/76561198882972479#!/compare/1551484800/1551571200

https://backpack.tf/item/7414252657

X = 14

Sale 3:

Sold for Fountain of Delight Burstchester (Mini at 9.5 below) + 4 keys + some metal

Seller: https://backpack.tf/profiles/76561198176488293#!/compare/1551744000/1551830400

Buyer: https://backpack.tf/profiles/76561198445049721#!/compare/1551744000/1551830400

https://backpack.tf/item/7414252657

X = 14

Sale 4:

Sold for Vivid Plasma Sky High Fly Guy (Suggestion at 11.5 below) + Bruiser’s Bandana (~0.5)

Seller: https://backpack.tf/profiles/76561198317790700#!/compare/1551744000/1551830400

Buyer: https://backpack.tf/profiles/76561198176488293#!/compare/1551744000/1551830400

https://backpack.tf/item/7414252657

X = 12

Other Sales:

https://backpack.tf/item/7434448968 (#1)

https://backpack.tf/item/7414252657 (#2 & #3)

https://backpack.tf/item/7408906992 (#4)

https://backpack.tf/item/7437069864 - scammed

#1

Untraceable

https://backpack.tf/profiles/76561198391243090#!/compare/1551830400/1552003200

https://backpack.tf/profiles/76561198830125323#!/compare/1551916800/1552003200

#2

Bulk for Vivid Tavish’s Crown

https://backpack.tf/profiles/76561198445049721#!/compare/1551916800/1552003200

https://backpack.tf/profiles/76561198150307915#!/compare/1551916800/1552003200

#3

Untraceable

https://backpack.tf/profiles/76561198150307915#!/compare/1552003200/1552089600

https://backpack.tf/profiles/76561198047168424#!/compare/1552003200/1552089600

#4

Untraceable

https://backpack.tf/profiles/76561198111367018#!/compare/1546819200/1547164800

https://backpack.tf/profiles/76561198099731030#!/compare/1540425600/1546905600

Vivid Sky High:

https://backpack.tf/suggestion/5c9c6792678072198803cb97

Kill-a-Watt Herald’s Helm:

https://backpack.tf/suggestion/5c9c6cf3d3817233c064cb07

Fountain of Delight Burstchester Mini:

Sale 1:

Sold for 8 keys

Seller: https://backpack.tf/profiles/76561198146307127#!/compare/1551571200/1551657600

Buyer: https://backpack.tf/profiles/76561198445049721#!/compare/1551571200/1551657600

https://backpack.tf/item/4765104505

X = 8

Marketplace Sales:

https://marketplace.tf/items/30621;5;u3005

https://manic.tf/keyprice/?at=2019-03-03 - $19.39 / $1.79 = 10.83 keys

https://manic.tf/keyprice/?at=2019-03-07 - $19.39 / $1.79 = 10.83 keys

$10.89 went to a buy order, excluding.

X = 11 (2x)

Taking 8-11 (9.5)

Sellers:

https://i.imgur.com/kADLbm8.png

https://backpack.tf/item/7434448968 - 16 keys

https://backpack.tf/item/7414252657 - 16 keys

Sales at:

12

14 (2x)

17

17 looks like an outlier, and is countered by the sellers at 16. Excluding 16.

Going with 12-14.