Just so you know, the original 'mopeds' are pedal-start 50cc motorbikes that originated in Europe. That's what this site mostly deals with. Your Honda is a scooter; they just get mis-labeled as 'mopeds' because some state BMVs have gotten in the habit of calling anything 50cc or less a 'moped'.
As for your scooter, the deal is whether its an Elite E or an Elite SR. The former is pretty small and can rarely top 35 mph; the latter is a bit bigger, has a variated transmission, and can usually top 40 mph. $600 would not be a deal for an Elite E (which usually go for less than $500), but would be a decent price for an SR in good condition. Check out www.motorscooterguide.net for a good summary of Honda scooters.