There are 2 of these in existence, backpack.tf doesn't know about the other one (it's a secret to everybody ( ͡° ͜ʖ ͡°) ). Overpay is calculated in all instances.

http://www.tf2outpost.com/trade/13909288

Sold for Terror-Watt Tyranium Helmet(~10.9 buds)

http://www.tf2outpost.com/trade/14043443

Sold for Cloudy Bicorne(~11.3), outdated price

However, he sold this Cloudy Bicorne for a Bliz Crones(~8.5) + gifted Bliz Cranium(~1.5) + Cauldron Coppers(~1.3) + 1 bud = ~11.3 buds

Proof: http://backpack.tf/id/76561198048772514?time=1378537200

Therefore, he got ~11.3 buds out of the Disco Titanium Tower after it's all said and done. Alternatively the Bicorne is ~10.5 with overpay on its own.

http://www.tf2outpost.com/trade/14240803

Sold with Steaming Buckaroos(~12 keys) + 1 bud for Cloud 9 Headsplitter(~11.9)

10.9 - 1.6 = ~10.3 buds

http://www.tf2outpost.com/trade/14340528 (current owner) B/O 12 buds

http://www.tf2outpost.com/trade/11982895

Sold with Roboactive Birdcage(~4.2) + 1 bud for Cauldron Executioner(~13.8)

13.8 - 4.2 - 1 = ~8.6 buds - outlier

Proof: http://backpack.tf/id/76561198043381861?time=1371884400 -> http://backpack.tf/id/76561198043381861?time=1372143600

http://www.tf2outpost.com/trade/11980830

Sold with 2 buds for duped Beams Company Man(~14.1)

14.1 - 2 = ~12.1 buds

Proof: http://www.tf2outpost.com/trade/11914041

http://www.tf2outpost.com/trade/13806720 (current owner) - B/O 14 buds, no notable offers