Updating the price, my first suggestion is off due to price changes and it only using one sale. Also there are 2 now, it is no longer 1 of 1. They are both on outpost.

http://www.tf2outpost.com/trade/14107422

Sold for Self Made key(~4.8 buds)

One from my last suggestion is still new enough to be valid

http://www.tf2outpost.com/trade/13094054

Sold for 5 pure + ~9 keys in sweets = 5.4 buds

http://www.tf2outpost.com/trade/13568557

Quicksold for 4 buds

http://www.tf2outpost.com/trade/13728860

Not sure what it sold for(involved a Terror Watt Robo Yellow belt)

These are all the sales I could concretely pin down.