Are you nuts $53 !!! Even $20.
You mean to tell me that your local auto parts store has nothing comprable to the MB stuff to 'lube' the sun roof tracks. I'm a huge fan of sunroofs, had them in almost all of my vehicles(including half a dozen MB's)and have always kept the tracks clean and lubed with a bit of bearing grease-applied with a small brush or WD40, never had any problems, ever.
I know, MB is going to tell us that using anything else besides their 'Sun Roof Lube' that the tracks will fail and render the sunroof junk in a matter of months, right?