from my understanding, if a hat is offered on a trade and it goes through 1:1, no overpay required.

http://www.tf2outpost.com/trade/15195331

-a very new one at 3 buds

http://www.tf2outpost.com/trade/15017346

-guy above bought as a quicksell (2 buds, 3 keys)

(2.2 buds)

http://www.tf2outpost.com/trade/14458843

-stated his price is 2.5

-offered smoking reggaelator, SOLD

http://www.tf2outpost.com/item/440,1967706863,390,5

(2.2 buds)

http://www.tf2outpost.com/trade/13954139

-buyout of 2.5

SOLD: knifestorm gonzila (outdated price)

http://www.tf2outpost.com/trade/12862570

-buyout of 2.5

SOLD: stormy barnstormer + 0.5 buds(?)

(2.5~ buds)