Proof below.

5 month-old price.

Sales:

http://www.tf2outpost.com/trade/15083978

-wanted ~1.8 buds

-sold for 25 keys=~1.5 buds

http://www.tf2outpost.com/trade/15678736

-b/o of 2 buds

-sold/bought for this aces robo-glove: http://www.tf2outpost.com/trade/15712626

-~1.8 buds

http://www.tf2outpost.com/trade/15616002

-selling for 2 buds

-sold/bought for this planets robo-toque (unpriced): http://www.tf2outpost.com/trade/15603282

http://www.tf2outpost.com/trade/15515593

-b/o of 2 buds

-had accepted offer of spartan on this blizz hermes (outdated):

http://www.tf2outpost.com/trade/10531444

-1.3 buds

-offer of smoking billycock+stormy ketche+~3.5 keys (1.7)

http://www.tf2outpost.com/trade/15389386

-wanted 1.5 buds

-bought this blizz reggae: http://www.tf2outpost.com/trade/14953428

-1.4 buds

http://www.tf2outpost.com/trade/14833255

-b/o of 1.8 buds

-spartan+black paint sold for steaming noble

-black paint: http://www.tf2outpost.com/trade/15082794

-~1.4 buds

http://www.tf2outpost.com/trade/14816894

-b/o of 1.7 buds

-sold/bought for this mem leak sultan: http://www.tf2outpost.com/trade/14813289

-1.6 buds

Current trades:

http://www.tf2outpost.com/trade/15557616

-wants 1.6 buds, 2 weeks

-notable offers:

22 keys (1.4 then)

blizz lucky shot (1.3)

http://www.tf2outpost.com/trade/15752323

-wants 1.5 buds, 1 week

http://www.tf2outpost.com/trade/12584202 (old trade of owner, September but using this for offers)

-notable offers:

22 keys+dirty juju (1.4 then)

30 keys (1.4 then)

stormy hotrod (1.3)

Sales: 1.3, 1.4, 1.4, 1.5, 1.6, 1.8

Low end seems like it could be 1.3 or 1.4 and high end 1.5 or 1.6. 1.3-1.6 includes this range and with some offers at 1.3 and b/os of 1.5 and 1.6 on some trades this seems like a good range. Either way it's very close. However it's safe to exclude 1.7-1.8 from the range looking at b/os and how rare such offers come along. Unusual overpay and original prices used.