They're listed at $25 a piece (you would need 4). I placed an order through Irvine BMW parts. Although he did place the order, he warned me that his computer had shown 0 delivered through the US bmw dealer network. Perhaps, no one in the US had ordered them (or at least received delivery) at that point? Either way, he told me it would be about 4 to 8 weeks.
Current: F10 M5
Past: F10 550, E92 M3