Hot Dog

http://backpack.tf/item/312360873

Sale 1) Sold for 50 Keys

http://backpack.tf/profiles/76561198228852400#!/compare/1485043200/1485216000

Sale 2) Sold for 40 Keys

http://backpack.tf/profiles/76561198055063451#!/compare/1486771200/1486857600

http://backpack.tf/item/233801645

Sale 3) Sold + ~8 Keys of Items for a Green Energy Detective Noir (50 Keys)

http://backpack.tf/profiles/76561198215714424#!/compare/1488758400/1488844800

50 - 8 = 42 Keys

Sale 4) Sold + Duped Purple Energy Tippler's Tricorne for a Starstorm Slumber Cotton Head (70 Keys)

http://backpack.tf/profiles/76561198063233185#!/compare/1488758400/1488844800

The Tricorne is most likely less than 30 Keys, so this sale fits in the range.

http://backpack.tf/item/276986337

Sale 5) Sold for a Green Confetti Pyromancer's Mask + ~2 Keys of Items

http://backpack.tf/profiles/76561198092238060#!/compare/1483142400/1483228800

http://www.tf2outpost.com/trade/28688804 - Capped by the Buyout of 45 Keys