“Although USCIS does not charge a fee for this form,
the Department of State does charge a fee of $70 when the Affidavit of Support is reviewed domestically.
-This means NVC will charge the fee for review the form for consulate processing.
This does not apply when the Affidavit of Support is filed abroad. ”
-This means if the I-864 is filed from abroad, e.g. your parents in China file this form there to NVC, they do not need to pay this fee to NVC if your parents use consulate processing for the green card application.