You'll always find wide ranges of prices for most any part for any make. I don't know what the original Mercedes striker lists for, but I've purchased OE Mercedes ones for $25 each online. I just buy parts when I see them very reasonable. I have a good amount of original Mercedes spare parts on hand. That way, when I really do need something I don't get slammed on the price.

The strikers I've seen out there are usually Kratex and EZ. I don't know the durability of either, but they can be had for less than 20 bucks each. By the way, if you have to pay someone to diagnose and replace a striker, you may have the wrong car.