Did you send in the GPU to AMD directly or the Retailer/Vendor or Manufacturer of the GPU to RMA?
Also the price they are quoting may be Pro-rated price or the price you originally paid.
IF you live in the EU, then you are, by law, covered for 2 years Warranty by the Retailer. The Retailer is the one that determines what action they will take concerning your RMA of your GPU card.