Sale 1:

https://backpack.tf/profiles/76561198083134207#!/compare/1581724800/1581811200

https://backpack.tf/profiles/76561198184688357#!/compare/1581811200/1581897600

Sold for 21 keys

sale 2:

https://backpack.tf/profiles/76561198184688357#!/compare/1585612800/1586304000

https://backpack.tf/profiles/76561198267189538#!/compare/1585612800/1585699200

Untrace / QS

sale 3:

https://backpack.tf/profiles/76561198267189538#!/compare/1586390400/1586476800

https://backpack.tf/profiles/76561198301456164#!/compare/1586476800/1586649600

https://backpack.tf/profiles/76561198075868377#!/compare/1586563200/1586649600

Untrace

sale 4:

https://backpack.tf/profiles/76561198075868377#!/compare/1586649600/1586822400

https://backpack.tf/profiles/76561198421588327#!/compare/1586649600/1586736000

Sold for ~16 keys (trade made before marked)

sale 5:

https://backpack.tf/profiles/76561198421588327#!/compare/1586736000/1586822400

https://backpack.tf/profiles/76561198073242439#!/compare/1586736000/1586822400

Sold for 17 keys

sale 6:

https://backpack.tf/profiles/76561198073242439#!/compare/1586736000/1586822400

https://backpack.tf/profiles/76561198185241815#!/compare/1586649600/1586908800

bulk

sale 7:

https://backpack.tf/profiles/76561198185241815#!/compare/1586908800/1586995200

https://backpack.tf/profiles/76561198305494036#!/compare/1586908800/1586995200

Sold for 15 keys (QS)

sale 8:

https://backpack.tf/profiles/76561198378695573#!/compare/1577750400/1586476800

https://backpack.tf/profiles/76561198850274253#!/compare/1586822400/1586995200

QS

sale 9:

https://backpack.tf/profiles/76561198850274253#!/compare/1587772800/1587859200

https://backpack.tf/profiles/76561198998082956#!/compare/1587513600/1588032000

Untrace

sale 10:

https://backpack.tf/profiles/76561198998082956#!/compare/1588204800/1588809600

https://backpack.tf/profiles/76561198337734785#!/compare/1588550400/1588636800

QS

sale 11:

https://backpack.tf/profiles/76561198337734785#!/compare/1588636800/1588723200

https://backpack.tf/profiles/76561198022589417#!/compare/1588636800/1588723200

Untrace

sale 12:

https://backpack.tf/profiles/76561198022589417#!/compare/1588636800/1588723200

https://backpack.tf/profiles/76561198100484031#!/compare/1588291200/1588723200

Untrace

sale 13:

https://backpack.tf/profiles/76561198077934343#!/compare/1585180800/1587772800

https://backpack.tf/profiles/76561198305494036#!/compare/1587081600/1587168000

QS

sale 14:

https://backpack.tf/profiles/76561198305494036#!/compare/1587081600/1587168000

https://backpack.tf/profiles/76561198160856661#!/compare/1587081600/1587168000

Sold for ~16 keys

sale 15:

https://backpack.tf/profiles/76561199003356173#!/compare/1584921600/1585267200

https://backpack.tf/profiles/76561198125958792#!/compare/1585267200/1585353600

Sold with ~4 keys in sweets for GE Tailor

use there

sale 16:

https://backpack.tf/profiles/76561198125958792#!/compare/1585526400/1585612800

https://backpack.tf/profiles/76561198088775634#!/compare/1585440000/1585612800

Keys or Aussie, can't tell.

sale 17:

https://marketplace.tf/items/tf2/105;5;u61

$38.99 / $1.90 = 20.52 keys

Total sales @:

15, 16, 16, 17, 21, 21 keys

https://bot.tf/stats/listings/Y9Q7D170

note that buyer used to be at 15 keys, jumped to 17 keys somewhat recently.

taking 17 - 21 keys.