Sale 1-3:

https://marketplace.tf/items/tf2/139;5;u58

$55 / $1.80 = 30.56 keys

$48 / $1.70 = 28.24 keys

$43.99 / $1.75 = 25.14 keys

Sale 4:

untrace

https://backpack.tf/profiles/76561198177841415#!/compare/1571961600/1573084800

https://backpack.tf/profiles/76561198337734785#!/compare/1572048000/1572134400

Sale 5:

23 keys

https://backpack.tf/profiles/76561198337734785#!/compare/1575331200/1575417600

https://backpack.tf/profiles/76561198277294190#!/compare/1575417600/1576886400

Sale 6:

untrace

https://backpack.tf/profiles/76561198002757046#!/compare/1570752000/1570838400

https://backpack.tf/profiles/76561198984426561#!/compare/1570665600/1570924800

Sale 7:

untrace

https://backpack.tf/profiles/76561198363395191#!/compare/1570665600/1570752000

https://backpack.tf/profiles/76561198268949690#!/compare/1570752000/1570838400

Sale 8:

untrace

https://backpack.tf/profiles/76561198320774949#!/compare/1571011200/1571184000

https://backpack.tf/profiles/76561198146147833#!/compare/1570838400/1571097600

Sale 9:

21 keys

with 1 key for aces KE(21.5)

https://backpack.tf/profiles/76561198089664680#!/compare/1571184000/1571270400

https://backpack.tf/profiles/76561198146147833#!/compare/1571097600/1571270400

Sale 10:

untrace

https://backpack.tf/profiles/76561198089664680#!/compare/1571270400/1571356800

https://backpack.tf/profiles/76561198859721638#!/compare/1571270400/1571356800

Sale 11:

21 pure

https://backpack.tf/profiles/76561198040965000#!/compare/1572652800/1572739200

https://backpack.tf/profiles/76561198120747050#!/compare/1541548800/1572652800

Sale 12:

12 keys / untrace

https://backpack.tf/profiles/76561198120747050#!/compare/1573171200/1573257600

https://backpack.tf/profiles/76561198295061570#!/compare/1573171200/1573257600

Sale 13:

untrace

https://backpack.tf/profiles/76561198295061570#!/compare/1576281600/1576368000

https://backpack.tf/profiles/76561198313364985#!/compare/1576281600/1576368000

Sale 14:

25 pure

https://backpack.tf/profiles/76561198313364985#!/compare/1577318400/1577577600

https://backpack.tf/profiles/76561198449333838#!/compare/1577318400/1577404800

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

Sales:

21,21,23,25,28,31