try pricing both out with the same options you want on the BMW NA website. A lot is already included with the 4.8 that is an option in the 3.0 (so will have to select those on the 3.0 to compare apples to apples).

When i did this, my price diff was far less than $10k. Still haven't made up my mind if I want to buy one though 9but that's a different issue).