Sale 1:

Sold for Disco Beat Down Ze Goggles + 4 keys

http://www.tf2outpost.com/trade/27908723 - B/O of 35

Seller: http://backpack.tf/profiles/76561198067016966/#!/compare/1457251200/1457337600

Buyer: http://backpack.tf/profiles/76561198041228333/#!/compare/1457251200/1457337600

X = 20.5 + 4

X = 25

Sale 2:

Sold for Orbiting Fire Sober Stuntsman + Aces High Tam O’ Shanter

No outpost link

Seller: http://backpack.tf/profiles/76561198007850070/#!/compare/1458630000/1458716400

Buyer: http://backpack.tf/profiles/76561198056191954/#!/compare/1458457200/1458716400

X = 11 + 14

X = 25

Sale 3:

Sold in less than a day for Australium Minigun

No outpost link

Seller: http://backpack.tf/profiles/76561198138913274/#!/compare/1457337600/1457424000

Buyer: http://backpack.tf/profiles/76561198009424974/#!/compare/1457337600/1457424000

X = 20

Sale 4:

Sold with 7 keys for Purple Confetti Noble Amassment of Hats

http://www.tf2outpost.com/trade/27932339 - No B/O

Seller: http://backpack.tf/profiles/76561198041228333/#!/compare/1457337600/1457424000

Buyer: http://backpack.tf/profiles/76561198138913274/#!/compare/1457337600/1457424000

X + 7 = 25

X = 18

Sellers:

28 keys:

http://www.tf2outpost.com/trade/28098183 - 4 days

Sales at:

18

20

25

25

Not using the sale at 18, due to the nature of it

Sale at 20 happened in a day, and there are two sales at 25, which should be reasonable enough to knock out 20 from the range

Going with 25 flat