Difficult to answer. Once a smart is delivered through one of the various dealers, maintenance and repair prices can vary depending on how the dealers run their businesses. I would asssume that the wholesale parts prices coming out of the smart supply depot in Tulsa are the same, but labor rates and shop fees (maybe even mark-up rates) are up to the dealers.
There have been some transmission shifter glitches, but I don't think anyone has summarily busted a box yet.