Has anybody checked out Tirerack lately? It seems the replacement prices for the 18" run flats (sport line tires) run about +/- $300 now and are not as high as the E90 RFTs of years past. I remember replacing my first damaged tire on my previous E90 was an exercise in patience (nobody had them at the time) and willingness to pay ($500ish for the single tire). I have no complaints about the Continental RFTs on my current F30 and will likely just replace them with the same when the time comes.
2014 328d MSport
2013 F30 Activehybrid3 MSport (Gone)
2012 F30 328i Sportline (Gone)