If I was you, I'd have a 2-2.3 range - as you're basically increasing the price with only 1 sale. I think 2.5 is the outlier here, with people clearly selling for less.

http://www.tf2outpost.com/trade/13089817

Sellers claims to have bought his with a max (2.3)

http://www.tf2outpost.com/trade/15012163

Sold for Hearts Scotch Bonnet + Sweets (2.7) Outlier most likely

Also, for your solds, I only see closed trade, no clear proof that they sold for what they were asking. 2.6 for the high range does seem a tad high, but I feel like the hat needs a slightly bigger shift downwards. Downvoted for now.

http://www.tf2outpost.com/trade/15916831 - offered 2 buds + 4 keys, claims to have better offer in pure but ended up trading anyway

http://www.tf2outpost.com/trade/16025000 - max head for this hat

http://www.tf2outpost.com/trade/16226140 - sold for 2 buds + 4 keys

http://www.tf2outpost.com/trade/15012163 - sold for hearts bonnet (2.5-3, old price) minus 2 keys

Lots of sales at 2.2, it probably should be in the range.