Sale 1:

https://backpack.tf/profiles/76561198073040123#!/compare/1587600000/1587686400

https://backpack.tf/profiles/76561197993708178#!/compare/1587600000/1587686400

Bulk

sale 2:

https://backpack.tf/profiles/76561197993708178#!/compare/1587772800/1587859200

https://backpack.tf/profiles/76561198137329982#!/compare/1563580800/1587859200

sold for 12 keys

Sale 3:

https://backpack.tf/profiles/76561198048036906#!/compare/1585180800/1585267200

https://backpack.tf/profiles/76561198337734785#!/compare/1585180800/1585267200

Bulk / QS

Sale 4:

https://backpack.tf/profiles/76561198337734785#!/compare/1585785600/1585872000

https://backpack.tf/profiles/76561198079316843#!/compare/1581552000/1587600000

Sold for ~10 keys

Sale 5:

https://backpack.tf/profiles/76561198324276106#!/compare/1582416000/1582502400

https://backpack.tf/profiles/76561198133534437#!/compare/1582156800/1582502400

Can't accurately trace, sold for one of the two vampires...

Sale 6:

https://backpack.tf/profiles/76561198133534437#!/compare/1582502400/1582761600

https://backpack.tf/profiles/76561198425105766#!/compare/1582070400/1583712000

Sold for 11 keys

Sale 7:

https://marketplace.tf/items/tf2/427;5;u29

$29.99 / $1.72 = 17.44 keys <--- https://backpack.tf/item/1010235249

$29.99 / $1.69 = 17.75 keys <---- https://bot.tf/stats/listings/MXXEZR16 B/O of 14 keys, capping (note that listing disappears around the same time that hat is sold)

Total sales @:

10, 11, 12, 14, 17 keys

seller for 16 keys,

calling 17 high,

buyers up to ~9 keys,

calling 10 low to balance,

taking 11 - 14 keys.