Sale 1-3:

https://marketplace.tf/items/tf2/1116;5;u3031

$4.19 / $1.75 = 2.39 keys

$3.44 / $1.75 = 1.97 keys

$5.95 / $1.72 = 3.46 keys // https://backpack.tf/item/6715872006

Sale 4:

untrace

https://backpack.tf/profiles/76561198987900589#!/compare/1579219200/1579305600

https://backpack.tf/profiles/76561198951526653#!/compare/1579219200/1579305600

Sale 5:

Midnight Whirlwind The Trackman's Touchdown(2.7 keys)

https://backpack.tf/profiles/76561198951526653#!/compare/1581033600/1581120000

https://backpack.tf/profiles/76561198192484517#!/compare/1580947200/1581033600

Sale 6:

bulk

https://backpack.tf/profiles/76561198263801172#!/compare/1579996800/1580083200

https://backpack.tf/profiles/76561198132767478#!/compare/1579996800/1580083200

Sale 7:

2 keys + 5 ref

https://backpack.tf/profiles/76561198132767478#!/compare/1583020800/1583107200

https://backpack.tf/profiles/76561198146259385#!/compare/1583020800/1583107200

Sale 8:

bulk

https://backpack.tf/profiles/76561198055822245#!/compare/1583020800/1583107200

https://backpack.tf/profiles/76561198146259385#!/compare/1583020800/1583107200

Sale 9:

4 keys

https://backpack.tf/profiles/76561198055822245#!/compare/1583280000/1583366400

https://backpack.tf/profiles/76561198129355329#!/compare/1583280000/1583366400

Sale 10:

bulk

https://backpack.tf/profiles/76561198056974324#!/compare/1585267200/1585353600

https://backpack.tf/profiles/76561198129355329#!/compare/1585267200/1585353600

Sale 11:

bulk

https://backpack.tf/profiles/76561198031743044#!/compare/1585958400/1586044800

https://backpack.tf/profiles/76561198056974324#!/compare/1585958400/1586044800

Sale 12:

bulk

https://backpack.tf/profiles/76561198311400236#!/compare/1584489600/1584576000

https://backpack.tf/profiles/76561198147812356#!/compare/1584489600/1584576000

Sale 13:

untrace

https://backpack.tf/profiles/76561198311400236#!/compare/1584576000/1584662400

https://backpack.tf/profiles/76561198164729775#!/compare/1584576000/1584662400

Sale 14:

2 keys + 22 ref

https://backpack.tf/profiles/76561198164729775#!/compare/1584662400/1584748800

https://backpack.tf/profiles/76561198160637040#!/compare/1584662400/1584748800

Sale 15:

untrace

https://backpack.tf/profiles/76561198160637040#!/compare/1584748800/1584835200

https://backpack.tf/profiles/76561198252999692#!/compare/1584748800/1584835200

Sale 16:

untrace

https://backpack.tf/profiles/76561198252999692#!/compare/1585094400/1585180800

https://backpack.tf/profiles/76561198170980343#!/compare/1585008000/1585180800

Sale 17:

untrace

https://backpack.tf/profiles/76561198311400236#!/compare/1585094400/1585180800

https://backpack.tf/profiles/76561198170980343#!/compare/1585008000/1585180800

Sale 18:

untrace

https://backpack.tf/profiles/76561198311400236#!/compare/1585180800/1585267200

https://backpack.tf/profiles/76561198121830870#!/compare/1585267200/1585353600

===============================================================================

Sales:

1.95, 2.1, 2.4, 2.4, 2.7, 3.45, 4

buyers at 2.35 keys: https://imgur.com/a/wbEB3yX