You can only hope and wish that an enthusiast will give you that kind of money. It is not old enough to be a classic, and it is not a very unique car (many E36 M3's were built, particularly the North American version).
I have no idea how to accurately estimate this, but that car sold for under $40k brand new, 11 years ago. I think market value can't be much more than $20k. That doesn't mean that you can't get more for it (you have somehow managed to keep the mileage extremely low), but $50k is literally laughable. I say this because I literally laughed when i saw the original post.
Then again, I may be a jerk.
Good luck with the sale!
P.S. What kind of maintenance has been done on the car? It really is a special case.
20 is what you should expect at best, you might ask a little more and add in a OBO, but don't be surprised when the offers are at 20. Like has been said, very low miles so if you have the right paper work you could potentially get more than 20 for it from an enthusiast that has to have that car...but don't expect that to happen in a few weeks, it will take awhile for that sale to come through. It is a very beautiful car, good luck.