seller at $24 https://gyazo.com/f7adf762e9642aeda2b70940bfddb807

I wouldn't use the $30 sale unless you can get a picture of the exact sale, as 12 Keys could be 1 or 2 off.

https://steamcommunity.com/market/listings/440/Unusual%20Bottle%20Cap - Several sales on the same day for between $25 and $30

More sales:

https://backpack.tf/profiles/76561198197609521#!/compare/1568419200/1568851200 - Unknown amount on SCM

https://backpack.tf/profiles/76561198882886230#!/compare/1567900800/1568246400 - 9 Keys + 22 Refined (~0.5 Keys)

https://backpack.tf/profiles/76561198070684631#!/compare/1491350400/1569888000 - Unknown amount on SCM

https://backpack.tf/profiles/76561198139695263#!/compare/1569456000/1569542400 - Unknown amount on SCM

https://backpack.tf/profiles/76561198308772967#!/compare/1570060800/1570147200 - 8 Keys + 15 Refined (low outlier)

https://backpack.tf/profiles/76561198057511457#!/compare/1566345600/1566432000 - Bulk sale

https://backpack.tf/profiles/76561198259986634#!/compare/1569024000/1569369600 - Sold for 14 Keys

https://backpack.tf/profiles/76561198437335225#!/compare/1567123200/1567296000 - ?

https://backpack.tf/profiles/76561198032515384#!/compare/1567209600/1567296000 - ?

https://backpack.tf/profiles/76561198032515384#!/compare/1567296000/1567382400 - Added 0.5 Keys of Ref for a Terror-Watt Mmmph (9.5 Keys)

https://backpack.tf/profiles/76561198298473489#!/compare/1567900800/1567987200 - Bulk sale

https://imgur.com/a/PVddMyY - 12 Day Seller at 12.57 Keys

https://backpack.tf/item/8012623778

The Seller at 10 Keys below also seems to have sold, which would give us a sale ~10 Keys.

With sales at 9, 9.5, 10, ~12, 13, 14, 9 - 14 should work here.