Buyers:

http://www.tf2outpost.com/trade/25760735 - Buyer at backpack.tf price (middle price, 9 ref)

http://www.tf2outpost.com/trade/25641779 - Buyer at backpack.tf price (middle price, 9 ref)

Sellers:

http://www.tf2outpost.com/trade/25739801 - 9 ref

http://www.tf2outpost.com/trade/25745037 - Unbumped and young, Selling for high-end backpack.tf price(10 ref)

These are the only two valid sellers on OP, other ones are either unbumped, painted(almost all of them) or one which is asking for 12 keys because of his spells...

Sales:

http://www.tf2outpost.com/trade/25582993 - 8 ref, Provided by Hex.

Buyers at 9 ref support this to be a quicksell (sold after 1.5 day, Quicksell)

http://i.imgur.com/INEImc8.png - 10 ref, Provided by Hex.

Classifieds:

http://backpack.tf/classifieds/?item=Hero%27s%20Hachimaki&quality=1&tradable=1&craftable=1

1x7 ref

1x8.66 ref

3x9 ref

1x11 ref

Seller on classifieds for 8.66 ref is an unbumped seller for 8.66 ref on tf2outpost:

http://www.tf2outpost.com/trade/25742956

Conclusion:

Buyers at 9 ref and the fact that 8 ref was quicksold after 1.5 day shows 9-10 ref is more accurate.