Sale 1-3:

https://marketplace.tf/items/tf2/1107;5;u3031

$18.95 / $1.68 = 11.28 keys

$9.25 / $1.72 = 5.38 keys - buyer price: https://imgur.com/a/WUxGJkZ

$18.95 / $1.69 = 11.21 keys

https://backpack.tf/item/3543933547

Sale 4:

bulk

https://backpack.tf/profiles/76561198311297599#!/compare/1580342400/1580428800

https://backpack.tf/profiles/76561198859721638#!/compare/1580169600/1580428800

Sale 5:

10 keys

Static Mist Skullcracker(7.25) + ~3 key sweets

https://backpack.tf/profiles/76561198859721638#!/compare/1581206400/1581292800

https://backpack.tf/profiles/76561198223239048#!/compare/1580947200/1581206400

skullcracker: https://backpack.tf/suggestion/5e93b4de017525221957806d

Sale 6:

bulk

https://backpack.tf/profiles/76561198974289370#!/compare/1581638400/1581724800

https://backpack.tf/profiles/76561198223239048#!/compare/1581724800/1581811200

Sale 7:

untrace

https://backpack.tf/profiles/76561198020966788#!/compare/1578528000/1583798400

https://backpack.tf/profiles/76561198974289370#!/compare/1581811200/1581897600

Sale 8:

untrace

https://backpack.tf/profiles/76561198141319249#!/compare/1581206400/1581552000

https://backpack.tf/profiles/76561198005032783#!/compare/1581120000/1581206400

Sale 9:

untrace

https://backpack.tf/profiles/76561198365818531#!/compare/1575849600/1584921600

https://backpack.tf/profiles/76561198005032783#!/compare/1581638400/1581724800

Sale 10:

SCM

https://backpack.tf/profiles/76561198099132915#!/compare/1584057600/1584230400

https://backpack.tf/profiles/76561198141022709#!/compare/1583971200/1584576000

Sale 11:

3 keys + 18 ref - buy order: https://imgur.com/a/ML3OuCl

https://backpack.tf/profiles/76561198314211872#!/compare/1585958400/1586044800

https://backpack.tf/profiles/76561198099132915#!/compare/1585872000/1586044800

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

Sales:

3.5, 5.5, 10, 11, 11

3 month unsold at 10 keys: https://imgur.com/a/wv0Ob3y

with 3 sales at 10/11 its a common trading point, just not for this guy^