It depends.
RGs with the old Edge / lopro Edge systems can fetch a nice price. Why? Because the old Edge/LoPros are regarded as THE floyd system. Plus, since its a licensed floyd, you can interchange between licensed floyds and the OFR easily. I'll say, if you got an RG with the Edge system, and you changed the pups to dimarzios or something, you can go for up to 60% of the original. If its in dead mint condition and Prestiege series, even 70%.
The RGs with the TRS or non-Edge systems will fetch a much lower price. 40%?