Ncik, the running cost differential between a Roadster and +4 of the same age is fuel and road tax. The rest is much the same.
A Roadster won't do much more than 30mpg if driven as MMC intended. Road tax is about £285...
But unless you are driving 5K+ miles a year the difference in fuel cost is trivial.
Roadsters, as you have found, are between £30 and £40K depending on age and confdition. Depreciation is almost unmeasurable.
