Recently, I came across this dapper. I bought it for 86 keys (as previous owner has already suggested). But i think, i have a better range for it:

First, i got offered max + 2 buds (4.2) by Ballsbridge hotel

http://www.tf2outpost.com/trade/13251629

In the end

I sold it for SF Scatter + SF Sniper + SF Bat + SF Flame Thrower

http://imgur.com/yF61gEt

i.e. 2.7 + 1 + .9 + .6 = 5.2

In conclusion, I put the original price i bought as lower end (3.9), because i think real transaction should weight more than offers

and Overpay in item as the higher end (5.2 * .9 ) = 4.7