Possibly my longest suggestion ever. Don't think any hat has sold as crazily as this one in the last 60 days.

Sale 1: GE Winter Woodsman

https://backpack.tf/profiles/76561198024614290#!/compare/1534896000/1534982400

Taking only real applicable sale here and putting it at 105

https://backpack.tf/profiles/76561198047918122#!/compare/1535328000/1535414400

Sale 2: 95 pure + DBD tundra top

https://backpack.tf/profiles/76561198120467518#!/compare/1534982400/1535068800

DBD tundra = 43 keys

138 keys

Sale 3: 97 pure

https://backpack.tf/profiles/76561198083520022#!/compare/1537142400/1537228800

Sale 4: Spec Ks Aussie Scatter + Pro Ks Aussie Eyelander + Aussie sniper + DBD Bloke's bucket + Abduction hfoha + 25 pure

https://backpack.tf/profiles/76561198091179527#!/compare/1534550400/1534723200

Scatter - 23.5

eyelander - 30

sniper - 22

HFOHA - 13

https://backpack.tf/stats/Unusual/A%20Head%20Full%20of%20Hot%20Air/Tradable/Craftable/91

Taking 13, as taking quickbuys would round up anyhow

Bloke's bucket - 15.5

https://marketplace.tf/shopitem/m9s/181;5;u62/

$29, 15.5 keys

129 keys

Sale 5: 102 pure

https://backpack.tf/profiles/76561198061914564#!/compare/1534723200/1534809600

Sale 6: 117 pure

https://backpack.tf/profiles/76561198140010255#!/compare/1536710400/1536796800

Sale 7: Unable to mini a Roboactive Firewall Helmet.

https://backpack.tf/profiles/76561198219980724#!/compare/1537401600/1537488000

Sale 8: Unable to mini a 1/1 strange killawatt caribou.

https://backpack.tf/profiles/76561198261521812#!/compare/1536969600/1537056000

Sale 9: Unusable, unable to take minis on certain items

https://backpack.tf/profiles/76561198044203779#!/compare/1532649600/1532736000

Sale 10: Unusable, outlier

https://marketplace.tf/items/30976;5;u13

Clear outlier, seller at $224 at the moment.

EDIT 1:

https://marketplace.tf/items/30976;5;u13

Two new sales

Sale 11: 135k

$238 on 11/07

Sale 12: 137k

$239 on 11/16

Sale 13:

https://backpack.tf/profiles/76561198078777084#!/compare/1541721600/1541808000

Strange PE Coldsnap

Sale 14:

https://backpack.tf/profiles/76561198203307876#!/compare/1540684800/1540771200

Duped Scorching Whoopee + Stormy Ninja Hood + Proks aussie scatter

With these sales in mind, and shuffle's comment that 97 and 102 sales took a day, as well as GE woodsman at 105 being low, considering three outliers and taking lowest sale as sale six at 117.

Despite unsolds on backpack for lower than 138 there are still trades on marketplace to back up this sale point.

Sellers @ 140 for eight days.

Quickbuyers @ 78.

Seller @ 140 on marketplace

Taking 117-137

Cheers.