From my studies I have found that most people either sell at ridiculous prices for kill streaks and parts or they sell at 2.8 and not 2.9. Both take sometime to sell as they are high tier stranges but there are way too many selling at the lower price then the high price.

http://backpack.tf/classifieds/search/id/52d1ed374dd7b8715e8b4567

1 at 2.7 buds ~ 11 minutes

1 at 54 keys or 2.8 buds ~ 13 hours

1 at 55 keys or 2.8 buds ~ 3 days

Outpost ~

2.9

http://www.tf2outpost.com/trade/19024036 - 7 hours

http://www.tf2outpost.com/trade/18896900 - 6 days

2.8 buds

http://www.tf2outpost.com/trade/15843236 - 4 months

http://www.tf2outpost.com/trade/18916126 - 5 days

http://www.tf2outpost.com/trade/19017685 - 11 hours

http://www.tf2outpost.com/trade/18991271 - 1 day

http://www.tf2outpost.com/trade/18819183 - 1 week

http://www.tf2outpost.com/trade/18830811 - 1 week

http://www.tf2outpost.com/trade/18698640 - 2 weeks

http://www.tf2outpost.com/trade/19016309 - 12 hours

http://www.tf2outpost.com/trade/19008680 - 21 hours

2.5 buds

http://www.tf2outpost.com/trade/19030054 - 1 hour

Solds

http://gyazo.com/552fbce22ed2b9dbb58a6318ffded9b1 - 2.8

http://gyazo.com/58681874ff9c17028acc204605abca20 - 2.8

http://gyazo.com/a09e06568dc34d071485bcadd9b3f372 - 2.3 from steam market