This is not my area of specialty, however, over the years I have read *a lot* about the wisdom of using MB coolant due to the various use of metals in the M-B engine that get exposed to coolant.
I believe that the amount of money in question is insignificant between Prestone, Peak, etc. and M-B. My cars are M-B and I use M-B coolant. I have been served quite well with this approach and have suffered no coolant-related troubles in a combined 339,000 mi.