+1 on this, a point I was trying to make in the thread where I posted the May sales.
I only posted the figures for Audi, BMW and Benz for the simple reason that that was what was requested. I'm not going to (and I don't think anyone wants me to) reproduce the whole chart here. You could argue that a Bentley buyer might consider a Model S. That doesn't make a Continental GT as cross-shopped with the Model S as a 5-Series.
As far as the maintenance of a Model S over a comparable car; I've said this before here, and some don't want to see it, but there won't be that much difference, over the term that these types of buyers keep cars like this. Modern engines are fantastically well built, and last for several hundred thousand miles. So a Model S will skip some oil changes, and doesn't have emissions control systems. It DOES however have wheel bearing assemblies, ball joints, struts, brakes, and A/C compressor, power steering components, a cabin filter, light assemblies, a transmission, window regulator assemblies, motor mounts, a climate control system and God only knows how many sensors, switches and control modules. Oh and there's that 17" monitor right in the middle, that controls EVERYTHING, running unique software (can anybody say Fisker?). All of these components will be prone to failure or require service at some point, just as they do on every other car made.
By all accounts so far, the Model S is a fantastic car, and a remarkable achievement for Tesla. But to say that cost of ownership will be zero (or even close to zero) is naive.