As I go free...

SALE 1

Unknown

https://backpack.tf/profiles/76561198073167542#!/compare/1560384000/1560470400

https://backpack.tf/profiles/76561198010993339#!/compare/1560124800/1560470400

SALE 2

Sold to bot immediately after purchase (sale 1)

https://backpack.tf/profiles/76561198010993339#!/compare/1560124800/1560470400

https://backpack.tf/profiles/76561198333986358#!/compare/1560384000/1560470400

SALE 2

Bulk for dbd crones

https://backpack.tf/profiles/76561198115740663#!/compare/1563235200/1563321600

https://backpack.tf/profiles/76561198280357510#!/compare/1563235200/1563321600

SALE 3

Bulk for ge brotherhood

https://backpack.tf/profiles/76561198123623513#!/compare/1560902400/1560988800

https://backpack.tf/profiles/76561198105071091#!/compare/1560902400/1560988800

SALE 4

Sold for pfetti coldfront commander

https://backpack.tf/profiles/76561198105071091#!/compare/1562457600/1562544000

https://backpack.tf/profiles/76561197976392732#!/compare/1562457600/1562544000

Unpriced, since the only other sale for the commander is 18 keys, cannot use this here as it would be much too low. I cannot update the commander either as there are sales at 18 and 38. There needs to be a third sale to determine which is the outlier there.

Mini for commander

Sold for 18 keys

https://backpack.tf/profiles/76561198807425101#!/compare/1562371200/1562457600

https://backpack.tf/profiles/76561197976392732#!/compare/1562371200/1562457600

SALE 5

Sold with 6 keys for blizzardy hallmark + peace sign dead cone + logo heralds helm + dp archers sterling

https://backpack.tf/profiles/76561197976392732#!/compare/1562803200/1563062400

https://backpack.tf/profiles/76561198156375472#!/compare/1562976000/1563062400

https://backpack.tf/item/5606808186

https://backpack.tf/item/5856694305

Everything is outdated, taking minis for all of them.

14.5 + 10.38 + 12.5 + 8 = 45.38 - 6 = 39.38 rounding to 39 keys

b/o was 40

https://bot.tf/stats/listings/426P06ZY

Mini for hallmark

https://backpack.tf/suggestion/5d36ebf7d3817223c9269a3f

Mini for dead cone

MINI SALE 1

Unknown, looks like scm

https://backpack.tf/profiles/76561198105569337#!/compare/1561161600/1561420800

https://backpack.tf/profiles/76561198872442216#!/compare/1548806400/1563321600

MINI SALE 2

Bulk for mg ye oiled baker boy

https://backpack.tf/profiles/76561198117971944#!/compare/1562198400/1562544000

No usable sale for the dead cone, taking highest buyer price here.

https://gyazo.com/8ab1067ea9d0736316204d079b2877d6

10.38 keys

Mini for heralds helm

https://backpack.tf/suggestion/5d36e7f16780722f163d0609

Mini for archers sterling

https://backpack.tf/suggestion/5d36e512678072283319605e

SALE 6

Quicksold for 37 keys

https://backpack.tf/profiles/76561198156375472#!/compare/1563062400/1563235200

https://backpack.tf/profiles/76561198224648164#!/compare/1563148800/1563235200

Classifieds at the time of making this suggestion.

https://gyazo.com/58d94dd1daae6353c45cd3a5b25900ab

Sales at 37 and 39. Since 37 isn't too far off from 39, and sellers seem to show that this does need a drop, as well as buyers not countering 37, going to include 37. Taking a range of 37-39 keys here.