Increase after 2 years.

Sold for 14 keys

https://backpack.tf/profiles/76561198192602363#!/compare/1588809600/1588982400

https://backpack.tf/profiles/76561198306872661#!/compare/1588809600/1588723200

Unknown

https://backpack.tf/profiles/76561198080179568#!/compare/1590192000/1590278400

https://backpack.tf/profiles/76561198043962821#!/compare/1589587200/1590624000

Unknown

https://backpack.tf/profiles/76561198066369838#!/compare/1587859200/1587945600

https://backpack.tf/profiles/76561198841279602#!/compare/1587859200/1587945600

Sold for 12 keys + 53 refined

https://backpack.tf/profiles/76561198305494036#!/compare/1587340800/1587427200

https://backpack.tf/profiles/76561198066369838#!/compare/1587340800/1587427200

Rounds to 13 keys

Sold for 11 refined?

https://backpack.tf/profiles/76561198049378596#!/compare/1587340800/1588377600

https://backpack.tf/profiles/76561198305494036#!/compare/1587340800/1587254400

Something missing here.

Sold for 14 keys + 1 refined

https://backpack.tf/profiles/76561198717500373#!/compare/1584662400/1583971200

https://backpack.tf/profiles/76561198841279602#!/compare/1584230400/1584316800

Rounds to 14 keys

Unknown

https://backpack.tf/profiles/76561198975565852#!/compare/1584057600/1584403200

https://backpack.tf/profiles/76561198841279602#!/compare/1583971200/1584057600

Sold for 24.99 on both March 18, 2020 and May 24, 2020

24.99/1.69 = 14.78 rounding to 15 keys

24.99/1.88 = 13.29 rounding to 13 keys

https://marketplace.tf/items/tf2/30863;5;u30

https://backpack.tf/item/5809082653

Classifieds:

https://gyazo.com/7d374783c34e8741cfd671b0dfb65c6e

Sales are at 13, 13, 14, 14, and 15.

Taking a range of 13-15 keys here.