Unfortunately, you may have picked the wrong kind of car to back up into. The damage you caused may be greater than you like to recall, and the cost of repairs to bring the ferrari back to its pre-accident condition may be more than you have estimated. Still, $50,000.00+ sounds like a lot of money for what you have described as a "scratch" (even for a ferrari). You should ask you insurance company to provide you with a copy of the repair estimate to confirm that the damages claimed by the ferrari owner are in fact the result of the accident you caused.
Given that an oil change on some Ferraris may cost $750 or more, a scratched bumper can be very expensive. You are entitled to know exactly what the claim is and why it is so expensive--It is very possible that a whole new bumper will have to be imported--or at least the one scratched will have to be sent to Italy to be hand cared for.
The short answer is 'Yes'. If your insurance has put you on notice that the damages may exceed your policy limit, rest assured that the Ferrari's insurance company will look to you for the balance of whatever it is left unpaid by your insurance.
You should look to get yourself an attorney-look into your policy or ask you rep--some policies provide for an attorney at the insurance's expenses in such cases.
I hope this helps-
Disclaimer: Please note that this answer does not constitute legal advice. It is merely intended to provide general information and for entertainment purposes and is only for issues arising under Illinois Law. This answer does not create an attorney-client relationship. It is always advisable to contact an attorney directly to find answers based on the facts unique to your case.
If there is actual damage, you are legally responsible. Ask the car owner to get you a property damage estimate & take it from there. Litigation should be able to be avoided in this matter. Make sure you follow the rules of your car insurance policy.