Ebay does allow business sellers to deduct up to 50% from refunds if the item is not returned in the original condition.
If you are not happy with the refund you have received, you may need to discuss it with Ebay.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)