My first suggestion :)

These are being used on auctions websites like scrap.tf for 9 ref value when they are worth considerably lower

Sellers:

6 ref : -

- http://www.tf2outpost.com/trade/28692635

- http://www.tf2outpost.com/trade/28699817

6.33 ref :-

- http://www.tf2outpost.com/trade/24165257

- http://www.tf2outpost.com/trade/28706166

Higher prices:

8 ref + :-

- http://www.tf2outpost.com/trade/28026068 (8 ref)

- http://www.tf2outpost.com/trade/28706392 ( ~ 8.22 ref)

- http://www.tf2outpost.com/trade/28685748 (8.33 ref)

Classified:

Multiple sellers at 6.33 ref and below & Multiple buyers at 6.11 ref and below:

http://www.awesomescreenshot.com/showImage?img_id=2033990

http://backpack.tf/classifieds?item=Backpack+Expander&quality=6&tradable=1&craftable=-1&australium=-1&page=1

Well, that's all i have to say, please go easy on me.