Using last month.

Sale 1:

Sold for 3 keys + 14 ref

Seller: https://backpack.tf/profiles/76561198847672167#!/compare/1562457600/1562544000

Buyer: https://backpack.tf/profiles/76561198072014080#!/compare/1562371200/1562544000

https://backpack.tf/item/7428220751

X = 3.5

Sale 2:

Sold for ~4 keys in stranges

Seller: https://backpack.tf/profiles/76561198454615761#!/compare/1563494400/1563580800

Buyer: https://backpack.tf/profiles/76561198193553109#!/compare/1563494400/1563580800

https://backpack.tf/item/4473512989

https://i.imgur.com/p3VyUEP.png - B/O of ~3

X = 3

Sale 3:

Sold to a bot for 3 keys

Seller: https://backpack.tf/profiles/76561198307786202#!/compare/1561420800/1561507200

Buyer: https://backpack.tf/profiles/76561198334559541#!/compare/1561420800/1561507200

https://backpack.tf/item/6183144901

https://i.imgur.com/p3VyUEP.png - bot.tf confirms

X = 3

Sale 4:

Sold for 2 keys (buyer’s end) + 30 ref (seller’s end)

Seller: https://backpack.tf/profiles/76561198254605212#!/compare/1563753600/1563840000

Buyer: https://backpack.tf/profiles/76561198311498888#!/compare/1563753600/1563840000

https://backpack.tf/item/6205155869

X = 2.5

Other Sales:

https://backpack.tf/item/7428220751 (#1-3)

https://backpack.tf/item/6680104560 (#3)

https://backpack.tf/item/6205155869 (#4-6)

https://backpack.tf/item/3195487323 (#7)

https://backpack.tf/item/2788339913 (#8)

https://backpack.tf/item/2695108835 (#9, gambled afterwards)

https://backpack.tf/item/6183144901 (#10 & #11)

https://backpack.tf/item/3732393180 - marketplace

https://backpack.tf/item/6710823538 - marketplace

https://backpack.tf/item/3195487233 - marketplace

https://backpack.tf/item/7466599087 - mannco and scrap

https://backpack.tf/item/5557905367 - tradeit

https://backpack.tf/item/5336380507 - transferred to likely scammer fence

#1

Untraceable

https://backpack.tf/profiles/76561198072014080#!/compare/1562544000/1562630400

https://backpack.tf/profiles/76561198373047474#!/compare/1561680000/1562630400

#2

Untraceable

https://backpack.tf/profiles/76561198373047474#!/compare/1561680000/1562630400

https://backpack.tf/profiles/76561198003926663#!/compare/1562544000/1562630400

#3

Untraceable

https://backpack.tf/profiles/76561198215936791#!/compare/1562371200/1562457600

https://backpack.tf/profiles/76561198847672167#!/compare/1562371200/1562457600

Most likely sold for 2 keys and the ref on the buyer’s end. Asked lemons for confirmation, will keep this sale updated. (not that it would affect the range)

Edit: https://i.imgur.com/ZYf5QL2.png - confirmation of a 3 key + 1 ref purchase

#4

Untraceable

https://backpack.tf/profiles/76561198841279602#!/compare/1563321600/1563408000

https://backpack.tf/profiles/76561198210923887#!/compare/1562889600/1563408000

Everything else after this was also untraceable, but I can’t be bothered providing links for them because of the backpack loading error being unable to provide a recent backpack to compare to.

#5

Untraceable

https://backpack.tf/profiles/76561198454615761#!/compare/1563580800/1563667200

https://backpack.tf/profiles/76561198830746853#!/compare/1563667200/1563753600

https://i.imgur.com/p3VyUEP.png - labelled as 2 keys + 39.88 ref (~3)

#6

Untraceable

https://backpack.tf/profiles/76561198830746853#!/compare/1563667200/1563753600

https://backpack.tf/profiles/76561198254605212#!/compare/1563753600/1563840000

#7

Untraceable

https://backpack.tf/profiles/76561198830746853#!/compare/1563667200/1563753600

https://backpack.tf/profiles/76561198254605212#!/compare/1563580800/1563753600

#8

Untraceable

https://backpack.tf/profiles/76561198169867374#!/compare/1511222400/1562198400

https://backpack.tf/profiles/76561198044144189#!/compare/1562112000/1563580800

#9

Untraceable

https://backpack.tf/profiles/76561198139632682#!/compare/1563667200/1563840000

https://backpack.tf/profiles/76561198002186909#!/compare/1563667200/1563753600

#10

Untraceable

https://backpack.tf/profiles/76561197968633696#!/compare/1561334400/1561420800

https://backpack.tf/profiles/76561198454615761#!/compare/1561334400/1561420800

#11

Untraceable

https://backpack.tf/profiles/76561198182700766#!/compare/1562889600/1563062400

https://backpack.tf/profiles/76561198363395191#!/compare/1562889600/1562976000

#12

Untraceable

https://backpack.tf/profiles/76561198363395191#!/compare/1562976000/1563062400

https://backpack.tf/profiles/76561198392116091#!/compare/1562889600/1563062400

Marketplace:

https://marketplace.tf/items/tf2/1112;5;u3008 - sales seem to range around 2.5-3 keys in the last month. Not going to bother with them as they aren't going to affect the range here.

Sellers:

https://i.imgur.com/y5fgCH3.png

https://backpack.tf/item/2937139739 - ~2.8 keys

https://backpack.tf/item/6191834637 - ~2.8 keys

https://backpack.tf/item/6805430520 - 3 keys

https://backpack.tf/item/4473512989 - 5 keys

https://backpack.tf/item/2784845369 - ~5.2 keys

Sales at:

2.5

3 (2x)

3.5

Sellers less than 3, excluding 3.5, keeping 3.

3 flat isn’t going to work with the mentioned sellers. Keeping 2.5.

Going with 2.5-3.