I have quite a few JEM replacement bodies that are brand new, sanded, sealed and ready for paint. $170. Rear Routed, AANJ. Most people charge $165 for a bare wood one.
I have RG 570 necks and a 517 neck that will fit, all are like new, $195. I don't think you'll find a JEM body and Neck for $250 or less, a neck alone will cost almost that much.