My big problem with this is you are punishing the seller even after he made good on his return policy. Failing to get the details straight is your fault, not the sellers.
How can you presume to know the motivation of others? I presumed that you would not have made this post had your seller given you the 500e refund, you found that offensive and assured me you would have blasted him in the open forum anyway. You see how that works?
Try to remove emotion from these transactions. If the seller stands by his return policy that is all you can expect. That's why it is there. It is your responsibility to cover all the details of the transaction prior to to completing the sale.
There is a reason we don't see these "condition spats" on the forum every day, we don't allow them. I'm sorry I let this one stand. As always, if you have a problem with a seller you can't resolve, please contact us.