Here is the quote I got from BMW for My M3 on just over 110k. I about spat my tea out when I first seen this but in hindsight with a 2k bill for a new SMG unit now it doesn't seem so bad.
Annual Payment
Driveline Warranty
Excess: £250
£2888.00 per year
Monthly Pay As You Go
Driveline Warranty
Excess: £250
£265.00 each month
Yeah, assuming the SMG AND something else expensive fails every year.