The Ground Controls are certainly substantial and very well made as I used to have a set. Some of the cost is down to custom machining to make the OEM BMW spring bearing fit. They also use decent NMB or Aurora bearings for the damper rod
It's because of the BMW bearing, they last for years. Some cheaper camber plates use cr@p bearings, which need replacing in a matter of months! I've also been down that road as well
As you can obviously tell, I defo recommend them, but £465 (via AKS) is crazy in this day and age. They are frickin good though