Tesla recovers a lot more of the individual vehicle cost as future R&D than Mercedes. That's probably a good thing as they are a start-up and Mercedes is a company delivering a few orders of magnitude more cars. Don't think it's a valid comparison though to say that Tesla is putting the money into tech and mercedes isn't.

Rather, Mercedes has access to better credit terms and availability than Tesla because they produce 100x more cars per year. And because of that, they don't need to recoup future R&D money from current cars. Ergo when you buy an expensive mercedes, more money goes into the car you bought than future cars.