Why not do a chargeback on your creditcard (or raise a PayPal claim)? The law is very clear, if an item is faulty or not as described the seller is on the hook for all costs. This includes return shipping and/or sending you a replacement.
A lot of sellers will try to strong-arm you but if you just do the chargeback/claim they have no option but to eat the loss. Creditcard companies and PayPal thankfully nearly always back buyers, tilting the power balance back to the consumers' side :)