Well, despite not having a Gen I, I can't see where you would have more than $600 in expenses every 5,000 miles, excluding major service such as tuneups - and $600 seems high to me. From a pure maintenance standpoint:<UL TYPE=SQUARE><LI>Oil Changes (2 every 6,000 miles) - $150
<LI>Tires (1/4 wear every 5,000 miles, thus 1/4 cost of four Pilot Sports) - $350
<LI>K&N filter cleaning kit - $15
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While Steve's costs reflect a rental car (which I would argue would be the single most abused Viper on the planet), many of us "vigorously exercise" our Vipers as well. While I have had some warranty issues, my normal maintenance costs have been around $150 every 5,000 miles - oil changes only. If you are talking about warranty issues, as with ANY used car without a warranty, you are rolling the dice. I don't think oil leaks were as big an issue as head gasket problems on Gen I's. If the car you are considering hasn't had them replaced, you might want to price this into your calculations "just in case". If you want to look at long-term ownership and many miles (which I suspect is what Steve is doing with his calculations), price a tune up, clutch replacement, brake pad replacement (and possibly rotors if you are doing a lot of track events) and all the other things you would normally maintain on a sports car.
Overall, I think the Viper is a VERY solidly built car that can last for a very long time under some of the most brutal conditions. I don't think the maintenance costs are that much higher other than the fact you are "feeding" a couple extra cylinders (bigger oil pan, more spark plugs, etc.). Good luck in your search!
Chris