If the product defect is attributable to a lack of compliance, you will not have to bear any cost.
In the first six months from the purchase the Law provides that no costs will be charged for the verify of the lack of conformity, after this deadline the request of verification may be charged to expenses, which you will have to bear only in the event that for the specific defect, the compliance warranty is not applicable.
See “What kind of warranty do i have on my purchases” for the cases established for the recognition of the compliance warranty.