Problem with tail light on 2008 ML550. Mileage is around 50,000

What is your question?

My rear light would not work even when the bulb was replaced. Dealer says assembly has a grounding problem which the dealer will fix [doing both sides] with a work around but wants around $275 to do so. Is this a design defect or manufacturing defect? Has anyone else experienced this problem? My sense is that MB should cover this cost. Also, the cost for simply replacing one front parking light is around $175 due to the need to remove the light assembly, so labor is the primary cost. I am shocked as to the foregoing expenses. Any comments?