I can't understand why anyone would buy a new NSX from the showroom floor, unless by some sheer fluke it was the exact spec that they would have configured themselves, and at a discount, and been available months before their made to order car was available. The chances of this happening a virtually nil, so it is not worth going into.
Demonstrator cars should be exactly that - for demonstration only, not available for sale for at least a year, if not longer. This would encourage people who insist on driving the car first before placing an order actually do that - place an order. The demo car should then be available for more people to do the same. If the demo cars are sold, then there won't be a car for people to sit in and drive before ordering - this will surely hurt future sales.
The new NSX was / is marketed as built to order, and to be specced by the customer. Allowing a demo car to be sold kind of spoils that part of the transaction, ruining the exclusivity and status of the NSX.