Re-suggestion, thanks to Torb for the info!

Sale 1:

https://backpack.tf/profiles/76561198039731024#!/compare/1523923200/1524009600

Untraceable.

Sale 2:

https://backpack.tf/profiles/76561198039731024#!/compare/1524096000/1524182400

https://backpack.tf/profiles/76561198214188676#!/compare/1524096000/1524182400

Bulk

Sale 3:

https://backpack.tf/profiles/76561198214188676#!/compare/1524182400/1524355200

https://backpack.tf/profiles/76561198253606754#!/compare/1524355200/1524441600

Sold for Bubbling Whoopee Cap + ~1 key in sweets.

Cap Mini:

https://marketplace.tf/items/174;5;u34

Sales for 25.5, 17.2, 21.45

Keys at 1.95, 1.97, 1.96

Totals are 13.08, 8.73, 10.94 keys

Taking 11 keys flat.

Total is 12 keys.

Sale 4:

https://backpack.tf/profiles/76561198153806405#!/compare/1524355200/1524441600

Sold for 12 keys.

Sale 5:

https://marketplace.tf/items/30316;5;u12

Sold for 20 USD

Keys at 1.97

Total is 10.15 keys

Taking 12 keys.

10 is closer to buyers than Sales.