There is no cost to you for donating your embryos. It is your gift to the family you choose to place with!
The costs of the process are paid by the adopting family, similar to all other forms of adoption. Some donors are curious about whether or not they can expect reimbursement for some of their IVF or storage costs. Most programs do not provide reimbursement for IVF and storage costs.
After you have placed your embryos with a family and signed the contractual agreements, the embryos become their responsibility and ongoing storage costs are theirs to pay.