Sale 1:

Sold for 24 keys (ID’s match)

Seller: https://backpack.tf/profiles/76561198035884807#!/compare/1513209600/1513296000

Buyer: https://backpack.tf/profiles/76561198085147012#!/compare/1513209600/1513296000

X = 24

Sale 2:

Sold for 24 keys

Seller: https://backpack.tf/profiles/76561198192850398#!/compare/1511481600/1511568000

Buyer: https://backpack.tf/profiles/76561198271728456#!/compare/1511568000/1511654400

X = 24

Sale 3:

Sold for 22 keys

Seller: https://backpack.tf/profiles/76561198341969000#!/compare/1515888000/1515974400

Buyer: https://backpack.tf/profiles/76561198285172916#!/compare/1515888000/1516060800

X = 22

Sale 4:

Sold for 21 keys + 1 ref

Seller: https://backpack.tf/profiles/76561198133242690#!/compare/1514246400/1514332800

Buyer: https://backpack.tf/profiles/76561198160468738#!/compare/1514246400/1514332800

X = 21

Sale 5:

Sold for 20 keys

Seller: https://backpack.tf/profiles/76561198011321852#!/compare/1514246400/1514332800

Buyer: https://backpack.tf/profiles/76561198221421520#!/compare/1514246400/1514332800

X = 20

Sale 6:

Sold in less than a day for 19 keys

Seller: https://backpack.tf/profiles/76561198002757046#!/compare/1514332800/1514419200

Buyer: https://backpack.tf/profiles/76561198200970331#!/compare/1514332800/1514419200

X = 19

Sale 7:

Sold for 16 keys + ~1 key in items

Seller: https://backpack.tf/profiles/76561198068701324#!/compare/1516838400/1516924800

Buyer: https://backpack.tf/profiles/76561198163258879#!/compare/1516838400/1516924800

Lower than quickbuyers, excluding.

Sale 8:

Sold for Bubbling Human Cannonball + 7 keys

Seller: https://backpack.tf/profiles/76561198132226518#!/compare/1517356800/1517443200

Buyer: https://backpack.tf/profiles/76561198251471500#!/compare/1517356800/1517443200

Should easily fit in the range.

Sale 9:

Sold with 4 keys for Miami Slick

Seller: https://backpack.tf/profiles/76561198250775142#!/compare/1512432000/1512604800

Buyer: https://backpack.tf/profiles/76561198081407695#!/compare/1512345600/1512604800

Should be used on the Slick.

Sale 10:

Sold for Terror-Watt Vintage Merryweather + ~9 keys (at the time) worth of items

No outpost

Seller: https://backpack.tf/profiles/76561198081407695#!/compare/1512604800/1512691200

Buyer: https://backpack.tf/profiles/76561198171659081#!/compare/1512604800/1512691200

This’ll be a large outlier without a B/O cap. Excluding.

Sale 11:

Bulk

Seller: https://backpack.tf/profiles/76561198119057660#!/compare/1513036800/1513123200

Buyer: https://backpack.tf/profiles/76561198035884807#!/compare/1513036800/1513123200

Sellers:

https://i.imgur.com/Xs3i5Hz.png

22 keys:

https://backpack.tf/item/2116714428

https://backpack.tf/item/260719349

https://backpack.tf/item/223884144

32 keys:

https://backpack.tf/item/918554266

Sales at:

19

20

21

22

24 (2x)

19 quicksold, excluding 19.

Going with 20-24.