To save the effort of unnecessary research on my part, could you elaborate on the build quality or design issues - I’m not particularly convinced that this would have had much to do with sales of the R-class though. I doubt many people who were in the market for one of these would have known (or cared!) where the factory was located
Certainly the late 90s/early 00s period was not MBs finest point for build quality (rust, electrical issues etc) - but that was nothing to do with where the cars were built and a lot more to do with design and specifications of materials and processes etc (paint and bodywork wasn’t great for a start - and I’m not on about the R-class!). Still that didn’t seem to affect sales a great deal and certainly not in the long term?
You touched on the issue of cost, and I still think that along with the aesthetics were the biggest challenges to sales. Who wanted to spend c. £80k (?) on a thirsty SUV type car that was neither an S-class in terms of luxury, ML in terms of purpose or E-class estate in terms of practicality? A G-class is no better but a good few people buy those for the image and looks. My GL63 is quite thirsty but for me is a good fit in terms of space, pace and seating capacity. If I didn’t need as many seats I’d still be driving an E-class with an AMG engine no doubt
I guess a £30k people carrier and £50k sports car may be better suited to people who want to cover those bases over two separate vehicles but that’s the nice thing about MB and AMG - plenty of choice of models to suit all kinds of lifestyles