Some people say, "If you have to ask how much, you can't afford it." Jesus Christ taught a different lesson:
If your friends are like mine, they'll mock the daylights out of you. Not wanting to be mocked, you may want to know - What does it cost? Not the selling price of the car, but what does it cost to own one? To drive one for a few years and have regular maintenance performed, that is what's important.
I know people who've run out and bought Porsche 928's because they thought they could afford one. 928's are an inexpensive purchase. Keeping one running is a different story. A single headlight for a 928 is $350. Depending on the year, complete Sach clutch kits run from $750 to $1,000. 928's have two mufflers. For a 1986 model, the center one is $2,000, and the rear one is $1,000. The catalytic converters are $3,200. Those are prices for parts from a discount house, and installation is extra. I'm sure Porsche dealers charge a lot more for parts and labor.
In general, it costs a lot less to keep a Mercedes-Benz running than a Porsche 928. However, after buying a Mercedes-Benz, it will cost something to maintain it. This comes as a shock to some people - "The most expensive place to have a Mercedes-Benz repaired is not the dealer." The most expensive repair that can be made will be by some graduate of the Shade-Tree Institute of Auto Repair. They'll take the car apart, try to figure out how it works by "looking at it", almost put it back together, charge more than they originally agreed to, and then give it back. It'll be undependable, run bad, and provide the owner with a constant source of aggravation until one of two things happen; it's properly fixed, or it's sold.
At that point, getting it properly fixed won't be the easiest task. Think about it. The next mechanic has to figure out what the previous nitwit did wrong, and correct it. How is the good mechanic supposed to find everything the last guy did wrong? The new guy has no idea what the last guy touched. The bad mechanic could have unplugged every subsystem on the car. Your new mechanic will have to look for clues and "guess". Now you need a mechanic who's both a detective AND a skilled repairman. You may want to save yourself a lot of aggravation and only let trained mechanics work on the car. I've found that paying someone to learn on my car is rarely profitable.
If you can't find a good independent, a dealer may be the best bet. So what does a dealer charge? It depends on the dealer. Dealers are independently owned and the prices vary. Regular customers get better deals, so your neighbor may pay more or less than you do. However, once you've been to the dealer, and entered your email and street address on their forms, they'll send you "useful spam" - discounts on parts and service.
Here are some prices I've received from my local dealer:
Aside from doing the job right, another benefit at my local dealer is when the service is complete, they wash and vacuum the car.
Some people can perform basic repairs themselves. For those people, here are the prices of some basic parts:
As expected, dealer prices are usually higher. However, dealers use original equipment parts. If the original part lasted 100,000 miles, then the replacement part from the dealer will last just as long - if not longer. The part will typically last longer if it was upgraded during the course of production. In some cases, dealer parts are less than those of a discount house. This is especially true if the dealer gives MBCA (Mercedes Benz Club of America) members a discount. If you're unfamiliar with MBCA, it's $45 per year to be a member. After joining and receiving your membership card in the mail, many dealers will give you a discount on parts and labor. I bought a set (16) of sparkplugs for my CLK430 from my local dealer, and the MBCA discount on those plugs was a lot more than the MBCA annual dues.
In looking at this list of parts, alternators and starters stand out. The dealer price listed is for a brand new part. The aftermarket price that you see is for a rebuilt part. Alternators and starters can be rebuilt for under $100 retail. Many parts supply houses have the core rebuilt at a wholesale price, and then lists it for the price you see. There is a lot of profit in selling rebuilt alternators for $300. Personally, I remove alternators and starters and have them rebuilt . It takes about an hour.
I believe "What does it cost?" is one of the more sensible things a person can ask.