Prices are all over the place. You can find them everwhere from $17K to $30K (good luck!)
The search I did on Autotrader had around 100 listed nationwide with an average of around $23K. I compared this to the Z4 and Audi TT. Both had an average price of $28K (2005) only.
I don't think the SRT6 is doing that much worse than similar cars. It is a high perf 2 seat toy. In this economy it is not going to be a world beater. Let things stabilize a little and so will resale values.
I think in 20years the majority will have disappeared. At that time a good one might fetch $20K plus, who knows. I bought mine to keep as long as I can. Smiling all the time!