I know the current price only have 24 hours but...

Classifieds: http://backpack.tf/classifieds/search/id/521e11874f96f4526c8b4567

1 for 7.5key

4 for 8key

2 for 8key + 5ref

5 for 9Key (3 unsolds for more than 1 day)

Now the proof:

7key:

http://www.tf2outpost.com/trade/14416055 (6key+3ref)

http://www.tf2outpost.com/trade/14417576 (7key+3ref)

http://www.tf2outpost.com/trade/14402354

http://www.tf2outpost.com/trade/14401575

http://www.tf2outpost.com/trade/14395711

http://www.tf2outpost.com/trade/14395352

http://www.tf2outpost.com/trade/14382598

http://www.tf2outpost.com/trade/14367030 (like 5-6 key)

8key:

http://www.tf2outpost.com/trade/14374189

http://tf2tp.com/trade.php?trade=9780108

http://www.tf2outpost.com/trade/14396594 (8key + 3ref)

http://www.tf2outpost.com/trade/14398051 (17h unsold)

http://www.tf2outpost.com/trade/14398002

http://www.tf2outpost.com/trade/14417015

http://www.tf2outpost.com/trade/14390198 (8key + 1ref) (22h unsold)

http://www.tf2outpost.com/trade/14368856 (8key + 4ref) (1day unsold)

9key:

http://www.tf2outpost.com/trade/14417853 (a few minutes ago)

http://www.tf2outpost.com/trade/14415442 (2h unsold)

http://www.tf2outpost.com/trade/14409865 (8h unsoldu)

http://www.tf2outpost.com/trade/14407402 (10h unsold)

http://www.tf2outpost.com/trade/14403184 (13h unsold)

http://bazaar.tf/trade/424560 (18h unsold)

http://www.tf2outpost.com/trade/14400866 (Sold!)

http://www.tf2outpost.com/trade/14397701

http://www.tf2outpost.com/trade/14396612

http://www.tf2outpost.com/trade/14395210

http://www.tf2outpost.com/trade/14392472

http://www.tf2outpost.com/trade/14389612

http://tf2tp.com/trade.php?trade=9780284

10key:

http://www.tf2outpost.com/trade/14303443 (5days unsold)

http://www.tf2outpost.com/trade/14309864 (2days unsold)

http://www.tf2outpost.com/trade/14383643 (1day unsold)

http://www.tf2outpost.com/trade/14383051 (1day unsold)

http://www.tf2outpost.com/trade/14218201 (1week unsold)

http://www.tf2outpost.com/trade/14355117 (2days unsold)

and a lot of more...

It's pretty easy to buy it at 8 keys, it's hard to sell at 9, and really really hard sell it for 10 keys.