I believe the adaptive cruise is probably more related to someone who does a lot of motorway mileage, helping to keep set distance etc. Rather than in general day to day traffic.
I know Scott like myself doesn't do a huge amount of motorway commuting, so its a big outlay for very little use. To be honest its unlikely it would recoup it when its sold on in the future.
As far as I'm aware the Cupra280 still comes with the normal cruise control as std, just non of the radar system for the adaptive kit.