Supply vs. Demand is key.
If you are trying to negotiate to purchase a replica Cobra from a company that has a 1-2 year waiting list, expect minimal savings and as already mentioned, maybe you can get a "package deal".
If you are trying to negotiate with a company that has an abundant supply or over supply, or dealers regularly selling their cars on eBay, you might have a better chance for negotiation and potential savings.
One other thing to remember, if you try to negotiate too much for a car on a long waiting list, don't be too suprised if your car takes a little longer to receive than you originally anticipated.
FYI: There are some very nice used cars out there too.
