Resuggestion, thanks to Cashew for the info!

Challenge 19, Team F.L.A.M.B.E.S!

80th suggestion, made by Beaser!

https://marketplace.tf/items/tf2/213;5;u7 - $25.99 / $1.91 = 13.61 keys

https://backpack.tf/item/7588292761

Sale #1 -

Untrace/Bulk

https://backpack.tf/profiles/76561198355796365#!/compare/1591401600/1591488000

Sale #2 -

Added 1 key for Stormy Swagman (12)

https://backpack.tf/profiles/76561198292137994#!/compare/1588982400/1589068800

https://backpack.tf/profiles/76561198188973946#!/compare/1588723200/1589068800

Sale #3 -

Bulk

https://backpack.tf/profiles/76561198292137994#!/compare/1588464000/1588636800

Sale #4 -

Untrace

https://backpack.tf/profiles/76561198045551697#!/compare/1588377600/1588464000

Revised Sales: (not in same order as above)

Sale 1:

https://backpack.tf/profiles/76561198157274202#!/compare/1591401600/1591488000

https://backpack.tf/profiles/76561198355796365#!/compare/1591401600/1591488000

Bulk

sale 2:

https://backpack.tf/profiles/76561198920070702#!/compare/1591401600/1591488000

https://backpack.tf/profiles/76561198157274202#!/compare/1591401600/1591488000

QS

sale 3:

https://backpack.tf/profiles/76561198147006723#!/compare/1587686400/1587859200

https://backpack.tf/profiles/76561198447257724#!/compare/1587686400/1587772800

QS

sale 4:

https://backpack.tf/profiles/76561198447257724#!/compare/1588291200/1588377600

https://backpack.tf/profiles/76561198045551697#!/compare/1587772800/1588377600

untrace

Sale 5:

https://backpack.tf/profiles/76561198045551697#!/compare/1588377600/1588464000

https://backpack.tf/profiles/76561198872796421#!/compare/1588291200/1588464000

https://backpack.tf/profiles/76561198124391666#!/compare/1588377600/1588550400

https://backpack.tf/profiles/76561198292137994#!/compare/1588464000/1588550400

untrace / bulk

sale 6:

https://backpack.tf/profiles/76561198292137994#!/compare/1588982400/1589068800

https://backpack.tf/profiles/76561198188973946#!/compare/1588723200/1589068800

Sold with 1 key for Stormy Swagger(12)

Total is 11 keys

Sale 7:

https://marketplace.tf/items/tf2/213;5;u7

$25.99 / $1.91 = 13.61 keys

https://backpack.tf/item/7588292761

Cashew's Part:

https://backpack.tf/item/6347826206 seller at 9 keys + 20 ref for at least a week.

Let's try 9 - 11 keys.