Treat a Viper like a commodity and you will get a commodity of a car. A Viper, that looks great at 20 ft, but that probably has lots of issues that would bother a particular person (badly scraped fascia, scuffs on the door and side sills from clumsy exit & entry, worn seat bolsters from dragging butt accross the seat rather than climbing in the car, questionable maintenance history, etc. Then you have to decide: "is it worth more for a better example?" That is where the price variation comes in and it is a personal decision.
I would rather have a well cared for 20,000 mile car than a neglected 2,000 mile car, too.