Yes, cosmetics might be cheaper for certain brands. Clinique on the other hand is much cheaper in the US and many Europeans love that stuff.
Sweet mustard should be easily available, if not in the same selection and variety as in Germany. Still, good call.
Hugo Boss would indeed be a bit cheaper, especially if you can get it at the Metzingen outlet.
For Leicas I have no idea. Watches are so-so. The high end can be cheaper in the US due to the exchange rate and the lack of sales tax as well as the possibility to buy online and grey market. Sinn is a bit cheaper in Germany. There might be models available that are indeed very hard to find in the US.
I didn't think of Class A and B Benz. Interesting. I was just amazed to see the C63 AMG at a dealer here for 93k Euro. That's basically $140k. That model starts at around $62k in the US, IIRC. And let's not even think about the price for insurance, tax and gas we pay in Germany. Ouch.
Sidenote: Today I polished my shoes with those Swiss waxes and yak hair brushes, I mentioned above. Very nice; very, very nice!
Till