Suggestion version 2.0 w/ fixed price ranges + updated buy and sell order values.

https://backpack.tf/classifieds?item=Tyurtlenek&quality=11&tradable=1&craftable=1&australium=-1&killstreak_tier=0

Buy Orders start at 3.49, ~3.5 keys.

Sell Orders start at 3.75 keys.

Bot.tf Sales:

https://ibb.co/SPnQvpX

https://ibb.co/NFVcCL2

1 Sold for 4 keys.

2 Sold for 3.95 keys.

1 Sold for 3.96, ~3.95 keys.

1 Sold for 3.66, ~3.65 keys.

1 Sold for 3.42, ~3.4 keys.

No viable Marketplace.tf sales.

SCM Sales:

https://ibb.co/g68Ps1Z

1 Sold for $7.51/ 2.34 = 3.2 keys.

1 Sold for $9.66/ 2.29 = 4.21, ~4.2 keys.

Excluding all other sales due to being either too low for current buy orders, or too high for current sell orders. Going with 3.65 keys solid.