Dan, I had mine done at my local MB dealer's parts dept. They asked to see the VIN and proof of ownership; they cost $26 each and they took about 3 or 4 days. Try Partshop first, though.
The laser cut keys are a nickel steel rather than the brass that most locksmiths would use. Less wear of the key, and presumably less brass coming off and plating the internals of the lock mechanism.