Didn't notice the last suggest or the comments about the stranges in one of the sales until after I did this one. Fixed that, which actually moved the range down a bit.

Sale 1

Sold for circling heart medic's mountain cap (50) = 45 keys

Seller before: http://backpack.tf/profiles/76561198019734628?time=1428649200 (April 10th)

Seller after: http://backpack.tf/profiles/76561198019734628?time=1428735600 (April 11th)

Sale 2

Sold for death at dusk salty dog (47) = 47* 0.9 = 42 keys

Seller before: http://backpack.tf/profiles/76561198075496482?time=1428390000 (April 7th)

Seller after: http://backpack.tf/profiles/76561198075496482?time=1428476400 (April 8th)

Sale 3

Sold/offered with strange awper hand (13) and ~5 keys in sweets for molten mallard spook specs (50-60) = 55 - 13 - 5 = 37 keys

Seller before: http://backpack.tf/profiles/76561198050571771?time=1427266800 (March 25th)

Seller after: http://backpack.tf/profiles/76561198050571771?time=1427526000 (March 28th)

Sale 4

Sold/offered with roboactive capo's capper (36) for duped burning milkman (76) = 76 - 36 = 40 keys

Seller before: http://backpack.tf/profiles/76561198086665332?time=1427612400 (March 29th)

Seller after: http://backpack.tf/profiles/76561198086665332?time=1427698800 (March 30th)

Sale 5

Sold for 36 keys, a pro ks collector's fan o war(~4) and a spec ks vintage lugermorph(~6.5) = 36 + (4 + 6.5)* 0.9 = 45 keys

Buyer before: http://backpack.tf/profiles/76561198050571771?time=1426921200 (March 21st)

Buyer after: http://backpack.tf/profiles/76561198050571771?time=1427007600 (March 22nd)

Mini for death at dusk salty dog:

Sold with searing plasma hot dogger (22-26) for amaranthine human cannonball (64-79) = 71 - 24 = 47 keys

http://backpack.tf/profiles/76561198094836185?time=1428217200 (April 5th)

http://backpack.tf/profiles/76561198094836185?time=1428303600 (April 6th)

Mini on duped burning milkman:

Guy who was selling it in the above trade had BO of 8 buds pure/9-10 in unusuals

http://www.tf2outpost.com/trade/25507673

8 keys at the time, so using that = 9.5 * 8 = 76 keys

There are a few more sales but these are all proving fairly close, so I think this is enough. Slocumruls commented also saying his earlier trade was much higher but tbh there are 5 trades here all in similar range so even if his is higher it's likely an outlier and I'm not spending hours figuring out a trade for unpriced and outdated hats when I think the amount of evidence here is enough to show what this is worth. If this is insufficient evidence, let me know and I'll have another look. Feedback welcome.