Hello, hi and lo (and greetings to mid as well, if he's anywhere around). Sorry to say, I can never predict what repairs at Schoeps are going to cost. It depends on what needs to be done, which they can't know until they disassemble your particular microphone or capsule. I also have to admit that I couldn't estimate a reliable average of the charges I've paid for capsule repairs; I'm a terrible businessman. I do send my repairs in through Redding Audio, though, to save on shipping and insurance costs, and I strongly recommend that approach.
But is there anything that leads you to suspect a problem with your MK 4V capsules? They shouldn't need any routine maintenance after a mere 10 years; try again in another decade or so. Of course if they've been dropped hard, or if liquids or dust have gotten into them, or if they make a rattling sound when you shake them, that's another story.
Only the three-pattern (MK 6) capsules, which they no longer manufacture, require regular maintenance as such. I happen to own four of those which were built in the 1970s; a trip to the Black Forest every 10 to 15 years has seemed to suffice for them. The majority of my other two dozen Schoeps capsules are over 20 years old by now, but I only send them in for checkup if I have some particular reason to suspect that they may need repair.
--best regards