Using last month.

The Sale:

Sold to a bot for 3 keys + 16 ref

Seller: https://backpack.tf/profiles/76561198436581726#!/compare/1552348800/1562803200

Buyer: https://backpack.tf/profiles/76561198340634356#!/compare/1562803200/1562889600

https://backpack.tf/item/5451891503

https://i.imgur.com/0UGt1bH.png - Bot.tf confirms

X = ~3.5

Other Sales:

https://backpack.tf/item/7769650971 (#1)

https://backpack.tf/item/7008027227 (#2)

https://backpack.tf/item/4729081007 (#3)

https://backpack.tf/item/5990262203 (#4 & #5)

https://backpack.tf/item/4605523956 - marketplace/not a sale. the player-to-player trade is the same bulk one I’ve seen last few unus taunt suggestions I’ve made.

https://backpack.tf/item/7115601811 - scammer/marketplace

https://backpack.tf/item/7774442541 - not unusual at the time

https://backpack.tf/item/4450852802 - mannco/gambled/scammer/not unusual at the time

#1

Untraceable, only 3 keys match

https://backpack.tf/profiles/76561198335791307#!/compare/1563494400/1563580800

https://backpack.tf/profiles/76561198366633096#!/compare/1562457600/1563580800

https://i.imgur.com/0UGt1bH.png - labelled as 4 keys + 4 ref

#2

Bulk

https://backpack.tf/profiles/76561198017954131#!/compare/1562630400/1562716800

https://backpack.tf/profiles/76561198061489334#!/compare/1562630400/1562716800

#3

Untraceable

https://backpack.tf/profiles/76561198343216628#!/compare/1563840000/1563926400

https://backpack.tf/profiles/76561198841279602#!/compare/1563840000/1563926400

#4

Untraceable, only 1 key + 3.33 ref matches.

https://backpack.tf/profiles/76561198340634356#!/compare/1562630400/1562716800

https://backpack.tf/profiles/76561198273803651#!/compare/1562544000/1562716800

https://i.imgur.com/0UGt1bH.png - labelled as 4 keys + 4 ref

#5

Untraceable

https://backpack.tf/profiles/76561198273803651#!/compare/1563580800/1563753600

https://backpack.tf/profiles/76561198363395191#!/compare/1563667200/1563753600

Additionally, no marketplace sales within the last month.

Sellers:

https://i.imgur.com/TOXS54E.png

https://backpack.tf/item/7084833398 - ~3.8 keys

https://backpack.tf/item/4405541531 - ~4.3 keys

https://backpack.tf/item/4729081007 - ~4.9 keys

https://backpack.tf/item/7008027227 - 5 keys

https://backpack.tf/item/5436217194 - 20 keys

Sales at:

3.5

And two untraceable sales recorded at 4 keys on bot.tf.

Given the seller at ~3.75 keys, it’s probably better to exclude the sales at 4 keys even if they were traceable. Additionally, the highest visible buy order is currently ~2.7 keys, which may indicate a further drop if that trading point were to become successful anyways.

Going with 3.5 flat.