Far from it. It is somewhat expensive to maintain though.
Tires are very expensive, it requires 8.5 quarts of synthetic oil, ~$20 oil filter, and parts are pricey.
It is basically a SLK32 AMG with a Chrysler designed body on it, so it will demand Mercedes-Benz pricing for repairs, parts, etc.

I'm not sure if a Mustang GT is more reliable, but parts, tires, and oil changes should be quite less.

Check the insurance rates too before you dive in to either.

Good luck.