I saw this on another post.
$544 each from getbmwparts.com p/n #13627838085
https://www.getbmwparts.com/parts/in...&siteid=214672
I have also heard that you can use M5 TA's and just take one piece of the existing M3 ones you are removing and make it work. Those are around 500 each I believe. VDO is the OEM manufacturer for these actuators. Good luck. I just did mine at 8 years, 60k proactively as I was putting a super charger on and getting to them later is a bitch.