Are you sharing a car in a different run group?
No, one of us runs Saturday, one of us runs Sunday - both in SM. Some regions want to charge 2, one-day fees, which many times is twice as much as the both days-one driver fee.
Not buying the insurance argument because some regions don't penalize for sharing and NASA lets us enter as a team with no difference in fees.
I know this issue doesn't effect many people so it's not a high priority - but it should be on the SCCA's radar if they want to increase entries.