Apologies to TNT Yoshi, as his suggestion is flawed in my opinion, but he has some proof which I plan to harvest from his trade. Plus I sold one of these.

Lower end:

Blizzardy Le Party Phantom + sweets

Le phantom is 2-2.5 buds, which comes to 2.025 buds with overpay included, however due to the sweets, most notably among which is a festive rocket launcher, I rounded this up to 2.1 buds.

http://tntyoshi.imgur.com/all/

Upper end:

Steaming Firewall Helmet + Nuts Bombing Run

Helmet is 1.8 - 2.3 buds, and the Bombing Run is 11 - 12 keys. taking median price and accounting for overpay we get 2.315 buds.

http://puu.sh/3GTjI.png

I bought my Capo for a Miami Nights Geisha, however this lacks a price so is unusable in this suggestion, unless I am mistaken.

Current owners on OP:

http://www.tf2outpost.com/search/133495613

Thanks for reading, please critique if you wish. Also could someone tell me if I was correct in thinking you should round off to the nearest half bud. Thanks.