Play his game and offer him INVOICE ONLY then...
I showed mine a copy of BMWconfig and stated that I had other dealers willing to do it for $200 over cost if I wanted to travel. He finally conceded.
The other thing missing from the BMWconfig "invoice" is the MACO cost which are $400 so if his Invoice is $400 higher than yours, that is the difference and yes, they can both be INVOICE (just with differing components). Some have gotten MACO waived, others have not been able to.