For comparison, look at the Lamborghini Gallardo. Looking at the sales number, Gen 3+ Viper production is at about 9500. Last June Lamborghini celebrated the 10,000th Gallardo. So that tells you something. You could take it a bit further and argue that the Gallardo is a global car and very few Vipers get exported thereby making the Vipers more concentrated in the United States and therefore less "rare" here. I would further argue however that Vipers are probably more disbursed over a wider geographic area (considering where the enthusiasts are located) versus the Gallardo which, while global, is still probably concentrated in major cities. So, speaking objectively I think you can safely say that gen 3+ Viper are "rare" in the United States, "slightly less rare" in and around major US cities and "exceptionally rare" outside the United States. I'm in the DC area and I probably see one once a month (not including the 4-20 that I see at my weekly events).