My 2 cents:
Tell them to send your money back first. (That's what you had to do to get the disks, right?) Once you have the disks and the cash, then the choice is up to you.
(If they can't prove the disks are real or any good, then why would they need them back?)
In reality, if you say that you want the cash back first, they likely will not pay. If they do, then they are either hoping you are gullible, or are just desperately hoping to ge ttheir disks back without getting reported. Either way, you will know what the real answer is without giving up any leverage.
Edit: One additional thought: Stardock's non-protection scheme may have actually provided more protection than the standard copy-protection scheme here. This may be a shop that churns out cracked games and copied movies. If they are used to the standard copy-protection schemes, then they think that they can just send out Stardock game copies and they will be home free. Little do they know that the real value in a Stardock game is the ability to log in and get updates - which cannot be done without the serial number...
(The possibility does exist that they are actually legitimate middle-men that themselves thought they had bought real disks from a vendor. If this is true, then you may get your money back. This may also explain why they have so many positive feedback items in their profile - they are generally good unless they get taken, themselves.)