There is one very inexpensive alternative that'll carry an MB on your typical coupe or sedan. I've done it before.
Use one of those $45 racks that sit on the trunk and have hold-down straps that hook onto the edges of the trunk lid.
They're not strong enough, really, for this job. So augment the rack with a lashing strap that runs into the cab and across the back seat. It'll 'settle' further up than that, of course. It'll be running just about where the backs of the head of the backseat passengers would be. And the "C" pillar of the car is then acting as a support for this weight over your bumper.
A downside is that your pedal, and other parts of the bike, can scratch paint on the rear deck of your car. But the contact points can be padded.
This works more than well enough on two lane roads at 50 mph. If I were on the interstate doing 70, then I'd probably use two lasing straps.