Proof below. 4 month-old price.

Sales:

http://www.tf2outpost.com/trade/16062603

-wanted 7 buds

-seems to have sold for ghosts baker (wasn't outdated during sale)+2 buds: http://www.tf2outpost.com/trade/15972909

-~5.7 buds

http://www.tf2outpost.com/trade/16002247

-wanted 7 buds

-seems to have sold for gbh honchos (quite outdated): http://www.tf2outpost.com/trade/16058685

-~7 buds due to the price, clear outlier with outdated price

http://www.tf2outpost.com/trade/16002247

-wanted 7.5 buds

-sold for disco ushanka+ghosts fro (very outdated)+planets l'inspecteur (very outdated)=~5.6 buds

-notable offers:

6 buds

Current trades:

http://www.tf2outpost.com/trade/17184197

-wants 6 buds pure, 1 month

-notable offers:

stash+2 buds for $280=~6

stormy phantom+pe pot=5.5

http://www.tf2outpost.com/trade/13951482

-recent notable offers:

disco noble+logo rack (outdated)=6.2 can't use for high end

duped burning trophy=~5.4

lantern cowl+16 keys=5.3

Sales: 5.6, 5.7, 7

I don't want to set 5.6 as low end with only a sale with outdated unusual prices for it, so using the 5.7 sale which is just 0.1 higher anyway. 6 comes from offers, take note the 'unsold' could have sold if he took the offer ~6.