With good maint that mileage is not too high. You need to remember though that good maint on a toyota with that mileage is not the same what a M3 should have. Besides regular oil/fluid changes etc, you should see some engine work by that point. Even if the car has been babied it should see some things already done on the engine around 100k miles. Also look for Inspection I and II's done by competent knowledgeable BMW mechanics. If you can speak with the mechanic that is even better. You will find that people that own M3s and have taken care of them will love to talk to you about these things and will be happy for you to talk to THE mechanic that has been doing these things.
I recieved full maint history with receipts with my M3 and I added the ones my mechanic did to that. I spoke with the mechanic who had been working on the car for 5 years who had a great reputation, he was able to tell me what his planned maint was for the car and confirmed that the owner had babied the car.
An abused M3 with any mileage on it can get to be an issue. A well maintained M3 is just like any other car. It may take a bit more to maintain it, but it will last and last.