Sale 1:

https://backpack.tf/profiles/76561198123995666#!/compare/1565568000/1567036800

https://backpack.tf/profiles/76561198225715416#!/compare/1569110400/1569369600

SCM

Sale 2:

https://backpack.tf/profiles/76561198080179568#!/compare/1563840000/1563926400

https://backpack.tf/profiles/76561198271547034#!/compare/1560816000/1563926400

Sold for 11 keys

Sale 3:

https://backpack.tf/profiles/76561198394877897#!/compare/1564876800/1564963200

https://backpack.tf/profiles/76561198402506689#!/compare/1556323200/1565049600

Sold for 13 keys

Sale 4:

https://backpack.tf/profiles/76561198402506689#!/compare/1565049600/1565222400

https://backpack.tf/profiles/76561198444936006#!/compare/1565136000/1565222400

Sold for 10 keys

Sale 5:

https://backpack.tf/profiles/76561198444936006#!/compare/1565136000/1565222400

https://backpack.tf/profiles/76561198100198172#!/compare/1565136000/1565222400

Sold for 12 keys

Sale 6:

https://backpack.tf/profiles/76561198840359034#!/compare/1565654400/1565740800

https://backpack.tf/profiles/76561198110930731#!/compare/1565654400/1565827200

Sold for HoS Vampire

use there

Sale 7:

https://backpack.tf/profiles/76561198110930731#!/compare/1565827200/1565913600

https://backpack.tf/profiles/76561198224648164#!/compare/1565827200/1565913600

Bulky

Sale 8:

https://backpack.tf/profiles/76561198224648164#!/compare/1566000000/1566172800

https://backpack.tf/profiles/76561198125791160#!/compare/1566086400/1566172800

Bulk

Sale 9:

https://backpack.tf/profiles/76561198125791160#!/compare/1566172800/1566259200

https://backpack.tf/profiles/76561198396149349#!/compare/1566259200/1566345600

Sold for ~13 keys

Sale 10:

https://backpack.tf/profiles/76561198337734785#!/compare/1563321600/1563408000

https://backpack.tf/profiles/76561198855132619#!/compare/1563321600/1563408000

Keys

Sale 11:

https://backpack.tf/profiles/76561198116799484#!/compare/1563667200/1563753600

https://backpack.tf/profiles/76561198402039752#!/compare/1563235200/1563753600\

https://backpack.tf/profiles/76561197968276434#!/compare/1563667200/1563753600

https://backpack.tf/profiles/76561198081172172#!/compare/1563667200/1563753600

https://backpack.tf/profiles/76561198078373457#!/compare/1563667200/1563753600

Gambling(?)

Sale 12, 13:

https://marketplace.tf/items/tf2/104;5;u30

$29.99 / $1.83 = 16.39 keys <-- https://backpack.tf/item/462543539 | https://bot.tf/stats/listings/MQ903R8Q B/O of 15 keys, capping

$15 / $1.80 = 8.33 keys <--https://backpack.tf/item/462543539

Total sales @:

8.33, 10, 11, 12, 13, 13, 15 keys

buyers up to 10 keys,

considering 12 resold for 10, then resold for 12....

taking 11 - 15 keys.