Sale 1-3:

https://marketplace.tf/items/tf2/110;5;u35

$45 / $1.78 = 25.28 keys

$45 / $1.68 = 26.79 keys

$54 / $1.69 = 31.95 keys

https://backpack.tf/item/1887213949

https://backpack.tf/item/1073762786

Sale 4:

untrace

https://backpack.tf/profiles/76561198130990555#!/compare/1581206400/1581552000

https://backpack.tf/profiles/76561198120747050#!/compare/1581465600/1581552000

Sale 5:

untrace

https://backpack.tf/profiles/76561198337734785#!/compare/1584144000/1584230400

https://backpack.tf/profiles/76561198089862063#!/compare/1583884800/1584230400

Sale 6:

max head - under buy orders

https://backpack.tf/profiles/76561198060379908#!/compare/1578441600/1579392000

https://backpack.tf/profiles/76561198809414908#!/compare/1579305600/1579392000

Sale 7:

bulk

https://backpack.tf/profiles/76561198809414908#!/compare/1579392000/1579478400

https://backpack.tf/profiles/76561198055622215#!/compare/1579392000/1579478400

Sale 8:

28 keys

27 keys + ~1 key of sweets

https://backpack.tf/profiles/76561198055622215#!/compare/1579737600/1579824000

https://backpack.tf/profiles/76561198130032444#!/compare/1579824000/1581120000

Sale 9:

untrace

https://backpack.tf/profiles/76561198130032444#!/compare/1585612800/1585785600

https://backpack.tf/profiles/76561198337734785#!/compare/1585699200/1585785600

Sale 10:

24 keys

https://backpack.tf/profiles/76561198337734785#!/compare/1585958400/1586044800

https://backpack.tf/profiles/76561198010332638#!/compare/1585958400/1586044800

Sale 11:

26 keys

25 keys + ~1 key of sweets

https://backpack.tf/profiles/76561198123185872#!/compare/1580688000/1581033600

https://backpack.tf/profiles/76561198111807532#!/compare/1580428800/1580688000

Sale 12:

untrace

https://backpack.tf/profiles/76561198123185872#!/compare/1582243200/1582329600

https://backpack.tf/profiles/76561198337734785#!/compare/1582156800/1582243200

Sale 13:

24 keys

https://backpack.tf/profiles/76561198060379908#!/compare/1582502400/1582588800

https://backpack.tf/profiles/76561198337734785#!/compare/1582502400/1582588800

Sale 14:

25 keys

https://backpack.tf/profiles/76561198134902030#!/compare/1578441600/1578614400

https://backpack.tf/profiles/76561198082378911#!/compare/1578528000/1578614400

Sale 15:

20 keys - under buyers

https://backpack.tf/profiles/76561198344291072#!/compare/1579824000/1579910400

https://backpack.tf/profiles/76561198082378911#!/compare/1579564800/1579910400

Sale 16:

untrace

https://backpack.tf/profiles/76561198101256571#!/compare/1584921600/1585094400

https://backpack.tf/profiles/76561198030058573#!/compare/1584835200/1584921600

Sale 17:

28 keys

24 keys + ~4 keys sweets

https://backpack.tf/profiles/76561198876360694#!/compare/1585353600/1585699200

https://backpack.tf/profiles/76561198030058573#!/compare/1585267200/1585353600

Sale 18:

untrace

https://backpack.tf/profiles/76561198336034192#!/compare/1585267200/1585353600

https://backpack.tf/profiles/76561198152373135#!/compare/1585267200/1585353600

Sale 19:

untrace

https://backpack.tf/profiles/76561198152373135#!/compare/1585440000/1585526400

https://backpack.tf/profiles/76561198117796848#!/compare/1585180800/1585440000

Sale 20:

even taking buy orders on these hats, the buyer sold belt for much less after this sale, therefore excluding

Blizzardy Storm Flipped Trilby + Orbiting Fire Sergeant's Drill Hat

https://backpack.tf/profiles/76561198117796848#!/compare/1585612800/1585699200

https://backpack.tf/profiles/76561198250999642#!/compare/1585612800/1585699200

Sale 21:

22 keys - under buyers

https://backpack.tf/profiles/76561198250999642#!/compare/1585699200/1585785600

https://backpack.tf/profiles/76561198284637591#!/compare/1585699200/1585785600

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

Sales:

24,24,25,25,26,26,28,28,32

buyers/sellers: https://imgur.com/a/meZgBRj

32 seems like high outlier