It all depends on whether you can actually find a buyer that wants it. Many piranha are very expensive when originally bought from a vendor. The price then takes a dive because it is hard to find someone who wants it. To give you an idea, a manueli comes in around $250-300,I got it second hand for like $175, but sold it to someone who really wanted one for like $400.
All supply and demand. Most people won't give you $50 for it, but if you can find the right person it might get your $300+ depending on size.