Im actually owner of one and for thanks giving i trade for this for a 7 bud unusual lololol

http://www.tf2outpost.com/trade/16064764 - appears to have sold for power surge tyrantium (6.5-6.8)

Outlier? Or maybe the 4 pure is an outlier...

First hat:

http://www.tf2outpost.com/trade/14820487 - 4 pure

http://www.tf2outpost.com/trade/14873190 - dbd noble was offered here

Offered close to 5 in pure

http://www.tf2outpost.com/trade/15910097 - added ~3 keys for a PS beak - http://backpack.tf/id/76561198049600807?time=1385798400 - offered on the beak, so no overpay. His b/o was 7, so it shouldn't be valued more than that

http://www.tf2outpost.com/trade/16064764 - PS tyrantium ~6.3

Next hat:

http://www.tf2outpost.com/trade/15868053 - sulph hwnn - unpriced

http://www.tf2outpost.com/trade/16064881 - sold in combo deal

http://www.tf2outpost.com/trade/16083406 - added 0.2 for a bubbling boa ~5.6

Next hat:

http://www.tf2outpost.com/trade/15511950 - hasn't been sold

Sales at 4, 5.4, 7, 6.3, 5.6. 4 and 7 look like outliers.