Somewhat of a counter, although the other guy closed his suggestion

Credit to Stephen King for sales 2 and 3

What I did:

Priced Bone dome:

http://backpack.tf/vote/id/5549a35bb88d88e7238b4570

Included this sale:

Sale 1

Sold for a Roboactive Bone Dome

(56.5*0.9) = 50.85 rounding to ~51 keys

http://www.tf2outpost.com/trade/25823913

http://backpack.tf/profiles/76561198053134374?time=1430204400 (April 28th)

http://backpack.tf/profiles/76561198053134374?time=1430377200 (April 30th)

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What he did:

Sale 2 (outlier)

http://www.tf2outpost.com/trade/25449600 B/o (40 Keys) 2 Weeks

http://backpack.tf/profiles/76561198106504211?time=1428735600

Kill-a-Watt Glengarry Bonnet: 16.5

Kill-a-Watt Thirst Blood: 18

16.5 + 18 = 34.5 ~ 35

Sale 3

http://backpack.tf/profiles/76561198053648692?time=1426230000

Midnight Whirlwind Taunt: I See You: 20

Aces High Crone's Dome: 38

20 + 38 = 58 * 0.9 = 52.2 + 4 = 56.2 ~ 56

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Calling 35 an outlier and taking the final range at 51 to 56 keys.