Okay, seems like a large bump, but let me explain myself before we get into this whole ordeal. I come bearing proof of my own, mostly from my own trade.

This unusual was 1 of 2 on the market, with my sale it is currently 1 of 1.

http://www.tf2outpost.com/trade/8405573 .

Sold today at B/O for 4 buds after 1 month of selling. 1 month is a fairly long time to keep an unusual, and that is why I am not raising the price to 4. It took a long time for someone to agree to pay my B/O (left no note on outpost, just added me). http://gyazo.com/68e44d5558ac6e2de36ffc898f8109bc (item history proof there)

Received several 3-3.5 bud offers:

Bizz Anger + Big Kill (about 3.5)

Green energy Salty dog (owner rejected offer of 3 pure)

Vivid Plasma Ye old baker boy + bud (was collecting, I believe he sold it before he finished his collecting) - 3-3.5 buds based on backpack.tf values for the Baker.

Countering the reason why it shouldn't go any higher: http://www.tf2outpost.com/trade/8864411 - buyout set at 4.5 buds, one offer in a week. I personally think that it received less offers because the KE in the trade took up most of the activity, but that is simply personal belief.

Hope I've provided enough evidence.