The only two twins I can think of which can be operated anywhere close to a high performance Single cost would be the Twin Commanche or, in terms of consumables, the DA42, which however has much higher maintenance costs due to the engines.
The Twin Commanche is probably the only twin which can be both purchased for relatively few money (50k to 100k$ for good ones) and which gives the operator a huge performance and range, particularly if equipped with long range tanks and Rajay Turbos. Figures I have read about are talking of 170 kt at 16 gph for the Turbo Twin Com or 150 kt at 15 gph for the normal one. Add to that 120 USG Fuel capacity and you get an airplane with a truely transatlantic range as well as the capacity to operate in avgas poor regions.
I do remember one Turbo Twin Commanche belonging to the editor of a German magazine which more than once did 10 or more hour trips including crossing the NATL from St. Johns to Guernsey.
15 to 16 GPH for a Twin @ 170 kt is really a lovely performance and not far away from airplanes equipped with the larger 500er engines.
One problem the Twin Com has however is that it is not de iced, or rather most of them are not and if so, they are still not FIKI approved.
The other one, the DA42, has of course the massive advantage of using Jet Fuel plus, at least the newer versions, also can do up to 170 kts of cruise. However, these are not "cheap to buy" airplanes. And, as one other poster said, while the DA42 has anti icing equipment, it can be an "interesting" airplane to fly under such conditions.
Senecas, I love them dearly and would have bought one when the chance arose until I did the math and figured out the horrendous fuel and maintenance costs as compared to my single Mooney. 24-30 GPH at 180 kts will put it in a league which most owner/operators simply have to fold. Add to that the relatively expensive engines in terms of turbos and overhaul costs, and you end up with 2-4 times the cost per hour. Convert one to Diesel and we are talking.