I don't think its worth it to be honest. But where could you get 5 decent brand name tyres for an F10 for €500?
Runflats for 18' or 19' are around €400 each, so 2 Runflats for €500 is also a stretch.

I would love to be proven wrong though! The last set of non Runflats 19' Pirellis I got for the 6 Series was €1,165. And that was a good deal at the time.