Enough that it's usually not worth it in a body that's also taken the years of use.

It's been a hot decade, but I think it cost $300 for Nikon to do substantial repairs to one of mine. And I think replacement cost was in the $500 range. Typical I think is in the range of 1/4 to 1/3 the cost of replacement for the whole camera... and if you like the model you've been using you can usually get a "used" model that has a double digit shutter count for around that same price by the time you've worn one out.

Ive been a working photographer for over 20 years and only had one shutter/mirror assembly ever go bad. it was on a canon 1ds mark II so it was a while ago, and it cost 300 bucks with a CPS discount.

I got an R3 back in early August of this year and I just checked I have just under 50 K shots on it. although thats a mirror less camera so, slightly different game.,