Good points from everyone, but here's the rub...
I have a quote on the Ram 3500 Dually - optioned like I want it - for $40,206. The RAM 2500 - with a whole bunch of stuff I don't need and don't want is $50,000. Both have the same engine. The dealers simply don't have entry price point RAM 2500's on the lot.
I bought a 2012 4 door 4x4 2500 diesel ST with cruise, tilt, power locks, windows, mirrors, bucket seats, etc for $38,000 in Port Lavaca back in June. They had about five just like on the lot to choose from. My previous truck was a 08 King Ranch F-350 so the dodge is not as fancy as the King Ranch but it is nice and comfortable and I like it.
I would not get a dually unless you absolutely need it. If for no other reason than just having to buy the tires. One thing also to watch out for on the dually's if you tow is that the GVWR on them is over 12,000lb. I don't remember what exactly it is 12,500 or 13,000 but this means if you hook up to a 14k rated trailer (which are very common) then you are over 26k and in CDL territory even if you don't weigh that much because they base the need of a CDL on if either your actual weight or rated weight is over 26k.