So ye, credit to MaGenta

Sale 1

http://www.tf2outpost.com/trade/21736471 - The Steaming Armored Authority (1 bud) was sold for a Disco Beat Down Medic's Mountain Cap.

Sale 2

http://www.tf2outpost.com/trade/22904682 - Sold for 1 bud.

Sale 3

http://www.tf2outpost.com/trade/22228777 - Sold for 41 keys = 2.5 buds

Sale 4

http://www.tf2outpost.com/trade/21959238 Sold for Aussie amby (1.15) + Aussie Tomislav (12 keys = 0.72 buds)

1.87 * 0.9 = 1.683 (rounding to 1.7)

Sale 5

http://www.tf2outpost.com/trade/21814255 Offered + Aces Robo-Pillar (~2.4) for Aces Crones (~5.3, seller had B/O of 5)

No overpay, 5 - 2.4 = 2.6 buds

Well, thx MaGenTa a lot for the additional proofs :P

Feel free to counter / support my proofs.