That's a question I'd first ask my escrow officer as they most likely deal with what is the 'standard' request by a lienholder. I was thinking it was about $150. Then I might ask an attorney. (prepaid legal services comes to mind for this...) Based on your response back below, it sounds like they have you over a barrel. Maybe before paying them anything, it should have been clearly defined what your original payment was to be applied to.
If they have a judgment, most can collect the amount of the judgment and 10%/year of interest payment. They can't just charge anything they want but it may need to be settled in court. An escrow officer can only execute agreed directions from parties, they don't make legal decisions.
And your comment that maybe you shouldn't have paid old debt...if they received a judgment and placed a lien on your property, it would have needed to be paid sooner or later....that's just the way it works. But they can't just arbitrarily blackmail you for more than the judgment declares. Good luck.