Just look at the classifieds: http://backpack.tf/classifieds/search/id/52000ecf4bd7b8f825000017 lots of people want to get rid of theirs for 6 keys, the supply is bigger than the demand, there's so many selling for 6 keys that 6.5 gets pretty irrelevant. And of course a suggestion is not a suggestion without proper outpost proof, so here you go:

http://www.tf2outpost.com/trade/14955974 6 key seller (2 days old)

http://www.tf2outpost.com/trade/14886702 unsuccesful 6.5 key seller (5 days old)

http://www.tf2outpost.com/trade/14967665 (6.5 key seller unsuccesful (2 days old)

http://www.tf2outpost.com/trade/14781701 7 key seller, not a single 6 key offer (week old

http://www.tf2outpost.com/trade/14953537 unsuccesful 6.5 key seller (2 days old)

http://www.tf2outpost.com/trade/14999642 unsuccesful 6 key seller (just 18 hours old tho)

http://www.tf2outpost.com/trade/14828783 5.8 key seller

http://www.tf2outpost.com/trade/14999554 6.5 key seller unsuccesful (this one also 18 hours.

http://www.tf2outpost.com/trade/15019226 6 key seller (5 hours old)

http://www.tf2outpost.com/trade/14919384 unsuccesful 6.5 key seller (4 days old)

http://www.tf2outpost.com/trade/14786053 unsuccesful 6.5 key seller (week old)

http://www.tf2outpost.com/trade/14991955 6 key seller (just a day old)

http://www.tf2outpost.com/trade/15019424 6 key seller (only 4 hours old)

http://www.tf2outpost.com/trade/14969449 6 keys (one sold within 2 days)

http://www.tf2outpost.com/trade/14601058 6.5 key seller (no buyers 2 weeks old)

http://www.tf2outpost.com/trade/14031537 not a single proper offer over 6 keys

http://www.tf2outpost.com/trade/14867510 6 key 2 ref seller unsuccesful (a week old)

http://www.tf2outpost.com/trade/14758442 6.5 key seller unsuccesful (week old)

http://www.tf2outpost.com/trade/15011459 1:1 bill's hat

http://www.tf2outpost.com/trade/14837699 another unsuccesful 6.5 key seller, week old.

http://www.tf2outpost.com/trade/14958101 6 key seller (2 days old)

http://www.tf2outpost.com/trade/15005151 6 key seller (15 hours old)

http://www.tf2outpost.com/trade/14906794 not a single 6 key offer

http://www.tf2outpost.com/trade/14922783 6 key seller (3 days old)

http://www.tf2outpost.com/trade/14980296 unsold at 6 keys (day old)

http://www.tf2outpost.com/trade/14786556 another unsuccesful 6.5 key seller (week old)

http://www.tf2outpost.com/trade/14780528 unsuccesful 6.5 key serller week old

http://www.tf2outpost.com/trade/14994446 6 key seller

http://www.tf2outpost.com/trade/14996409 1:1 bill's

http://www.tf2outpost.com/trade/15001133 5 key seller

http://www.tf2outpost.com/trade/15005057 6 key seller

I know it's not that much proof, but seriously, just check the classifieds. Everyone wants to get rid of theirs for 6 keys. No one's buying for 6.5 keys.