Just read through this thread, I find the tyre/tire issues bizarre. I live in Ireland where the roads are bad, whether weather conditions are very mixed and where cars generally lead a harder life. The 20" runflats on my 530d GT have been faultless.
Some years ago when alloy wheels were becoming popular I remember that some manufacturers had problems with 'porous' alloys where the air-pressure was leaking through the alloy metal. I could imagine that if the alloy painting or lacquering process was flawed that this could be possible. Demand 4 new wheels from your dealer and see if it solves the issue.
By the way BMW pricing in the US is incredibly competitive, you guys probably don't realise it but the average price of a BMW in the US is about 30% lower that the EU average!