It's sad as it is always the same people responding too negatively or positively; both using personal opinion and using that as factual information. "It's fair market." blah blah blah.
We aren't in econ 101 and ebay isn't the only place to buy a viper. I was just outside in my garage and was looking over my viper. To me, it is worth more than what I paid for it. That is all that counts at the end of the day.
Cars will go up in value given enough time. This car is timeless because of it's design and also because of the curves which always age better than edgy cars. Consequently, I think it is pretty illogical to think the viper will be excluded from eventual appreciation.
So basically, if you have to sell now, then don't ask what it is worth, find out yourself. Try Hemmings, AT, CL, kijiji and this site. Try your dealer as some people have better luck with dealers right now.
Finally, if people have to "sell now" it isn't necessarily an indication of car value. It could be that 20 year old kids finally got their "dream car" and realized they can't afford the ps2's and Viper Tax and are selling. It could mean that someone could afford the car and lost their job, is moving, is having a baby, is moving on up....etc. There are way more factors now than ever before that are prompting quick car sales and this isn't exclusive to the viper. When market conditions improve and people have more confidence in buying toys....you won't see beautiful rare and desirable cars like the OP has going for 30k.