Piggybacking this suggestion from Sports Demo's suggestion and Polar's advice.

Three proven sales in 2 months.

First Sale---------------------------------------------------------------------------------------------------------

Purchased one of these a few days ago - http://i.imgur.com/HFBB0Pt.png

Flies Yellow Belt (6)

Two Earbuds Pure (2)

Poisoned Shadow Gatsby (~4~)

All for a Flies Team Captain (12)

Not sure if overpay should be applied, and for that matter which hats it would be applied to.

My backpack can be checked to verify the unusual hat’s effects.

Second Sale ---------------------------------------------------------------------------------------------------------

Sold for a Haunted Ghosts Familiar Fez - http://www.tf2outpost.com/trade/19917459

5 * (0.9) = 4.5

Overpay applied as Fez was offered. Credit to Polar for sale found on previous suggestion.

Third Sale ---------------------------------------------------------------------------------------------------------

Sold for an Aces High War Pig + 2 Pure - http://i.imgur.com/jj3TJKb.png

( http://i.imgur.com/ha5aKEI.png | http://i.imgur.com/rcOfskL.png )

(3.8 * (0.9)) + 2pure = 5.42 (Rounded to 5.5)

Credit to Sports Demo for proof of sale, found on previous suggestions.

Not only does this seem an outlier, but oldest of all three trades.

Furthermore, as Polar pointed out, B/O on hat was originally 4.5, making any further payment overpay.

Therefore, range of 4 – 4.5 for the Poisoned Shadows Gentleman’s Gatsby.