Um, no, the 200 is advertised as the 'Seller's Listing Price' on the Sedo site and as the seller's 'Desired Price' in my control panel.
Seller's Listing Price
So I am at a loss how you can think it is 'reasonable' for someone to then come back with a 5000 price, in my opinion this is simply dishonest.
If it had been originally advertised at 500 I would have offered that although based on my first experience I would not be surprised if the seller then countered with 12500.
Greywing, I'd have agreed this may have been a defence if mine had been the first offer but there had been several offers before mine. So to me this shows the seller knew exactly what price was being advertised and that this was a deliberate decision by him/her.