So reading between the lines, it is expected that R230 SL running costs are going to similar to S-class vehicles of the same era?
Are 630i costs significantly lower? It seems that the SL is superior to the 6 series but are the running costs that much higher, are we talking 50% more, or 300% more? I can't imagine a 6 series is cheap to run, regardless of the spec.
The SL is a very much superior car, its suspension is absolutely sublime, as are the engines and feel of the whole thing. The Vario roof makes it a car for all occasions. The only obvious downside being the lack of rear seats which may be an issue (CL has rear seats and is very similar with a fixed roof which is a good alternative).
Ongoing costs are not horrific for the type of car IF you avoid the main dealer network.
The engines are absolutely bulletproof, you are unlikely to get an expensive problem even if you barely service them - they will outlast the car itself. Gearboxes are also very reliable, i rarely ever hear of one fail on the various mercedes forums, even at huge mileages. As per most auto's just keep on top of the fluid changes and it will go on and on.
Servicing is the same as any other car except for the increased count of service parts needed, a 500 takes 16 plugs and 8.5L of oil for example. All dead cheap stuff though obviously. The only other service area which i wouldn't personally let anyone other than a true specialist touch is the brakes, i am no techie when it comes to cars but they use some sort of active sensing system on the calipers which makes the pads very dangerous to touch yourself. Tyres, pads, discs etc are all normal for the type of car, approx £1000 for a set of decent tyres for example, so nothing out of the ordinary there either.
Only real real potential area for costs is the active body control. This is an absolutely superb system but it can have its issues. On the whole it is likely to require a new fluid compressor every (IME) 60-80k miles, and struts can fail as can various valves and pipes and things (Mine has had a new valve block, pump, and struts from memory). There are a lot of specialist rebuild options for the struts nowadays though. In my opinion worst case for an ABC failure (if you have the time to send the struts away for rebuild and can be without the car) would total no more than £2-3k nowadays. So it really isnt the big deal it used to be, i dont worry about mine at all.