No...they are being realistic. I am not here to rain on your parade, but these are subs that are $200 new per piece. So for you to ask $650 is like saying...Used subs = $300 and your box = $350?
Now to save you the hassle of bumping these on a regular basis, I will give you a solid recommendation. Start your pricing at $400 with the box local pickup. Or $400 shipped for the subs alone, or $350 + shipping.
I think that would be a great starting point for you to work from.