Maintenance on an M3 is NOT cheap and this one has everything done! Even the cooling system, which could have been done later, but gives the next owner a piece of mind and a car to just jump into and drive for quite a while before the next big bill arrive.
So, I'd say that's a good price for a knowledgeable buyer who looks behind just the headline numbers of model year and mileage.
Good luck with the sale!
But I will add another seed of doubt to your decision, I'm afraid. I've never driven an E92, but I bought my E46 M3 from a previous owner who switched to E92 M3. He told me that whenever I decide to sell the M3, he wants to buy it back.