BEH

Unless it is a 3 year lease when the car will be under warranty for the full term and then returned I personally would not purchase a demonstrator.
When I was shopping for my 2006 BMW, the salesman came with me on a test drive of a brand new vehicle that just that morning came off the truck.
It had 75 km on it.
Went to secondary roads just north of the dealership and he told me to "open it up".
We red lined it numerous times before bring it back to the dealership.
Didn't buy that car!
Just this week took a 2017 AMG 43 demonstrator for a drive, again with a salesman and again drove it very hard with his blessing and encouragement.
In my opinion not worth the savings.
Just my 2 cents.