Ok, so I guess I should clarify what I said. I was more so talking about cars in the SLK55 range and up to the SL550, not the SL55/SL63 AMG. In the US, the SL550 starts around 96K and the SL55 AMG at 130K. I'd tend to agree that a car in the low/mid 100's is really pushing the limits for a younger person unless they made great investments when they were just starting out or came from some money. As for the fields I specified, I was reaching for examples, maybe doctor and lawyer weren't the best choices.
You don't have to tell me about doctors, I went to Johns Hopkins for undergrad and my MSE and have multiple friends who were pre-med. One is at Yale Med right now for Neuroscience and he's still not done (8 years from start of undergrad). I also had another friend who ended up at Harvard Law after an accelerated undergrad career and is practicing somewhere in NY, but I don't really know how well he ended up (I'm assuming pretty well).
So, all I'm saying is that it's certainly possible for a "younger" person to splurge on a fairly expensive car, but it's definitely an exception to any norms.