Just as a comparison. I know a guy with the exact same bike, rebuilt motor had done 4 hours riding. Excellent original plastics, new clutch kit, good tyres etc. Just a good club level race bike (still had drum brake front end).
He tried to sell it for $2500 then $2200, then $2000 and eventually sold it on ebay for $1450 after about 2 months. Yes, $1450. Now whilst that is a genuine bargain IMHO, it give some perspective to the difficulty selling an 84 RM250 in the pre 85 250 class.
Note, I'm not telling you your bike is only worth that much, merely giving you some real data to help you with understanding the market for that model bike.
Cheers