Ah.

SALE 1

sold for 3 keys

https://backpack.tf/profiles/76561198387707377#!/compare/1558051200/1558137600

https://backpack.tf/profiles/76561198029431277#!/compare/1558051200/1558310400

only 3 seem to match up, probably more though.

SALE 2

sold for starstorm wide-brimmed bandito

https://backpack.tf/profiles/76561198029431277#!/compare/1560988800/1561248000

https://backpack.tf/profiles/76561198094720698#!/compare/1561248000/1561593600

bandito is outdated @ 6 months, taking a mini for it.

13.5 rounding to 14 keys.

b/o was also 14

https://bot.tf/stats/listings/M06O5EQM

mini for bandito

https://backpack.tf/suggestion/5d36dfead381721a3577bead

taking 13.5 keys

SALE 3

sold to stn bot

https://backpack.tf/profiles/76561198094720698#!/compare/1561680000/1561939200

SALE 4

sold for 12 keys

https://backpack.tf/profiles/76561198311498888#!/compare/1561939200/1562025600

https://backpack.tf/profiles/76561198107839402#!/compare/1561939200/1562025600

SALE 5

sold with searing reggaelator for stare from beyond kabuto

https://backpack.tf/profiles/76561198107839402#!/compare/1562025600/1562284800

https://backpack.tf/profiles/76561198143819507#!/compare/1562198400/1562284800

better used for one of the other two hats

SALE 6

sold to quicksell bot

https://backpack.tf/profiles/76561198143819507#!/compare/1562284800/1562371200

SALE 7

unknown

https://backpack.tf/profiles/76561198284348086#!/compare/1563321600/1563494400

https://backpack.tf/profiles/76561198337734785#!/compare/1563408000/1563494400

SALE 8

bulk for ghastly ghosts jr pomade prince

https://backpack.tf/profiles/76561198145896898#!/compare/1557532800/1557619200

1 marketplace sale

28 on june 21 (28 / 1.84 = 15.217 rounding to 15 keys)

https://marketplace.tf/items/tf2/359;5;u30

classifieds at the time of making this suggestion.

https://gyazo.com/c51e88d2dc3e006e2123d3e74bd3dab8

sales at 12 and 14. marketplace sale at 15. buyer at 12 suggests that 12 is low. taking a range of 14-15 keys here.