You have to pay. No fee waivers for this process. This is from USCIS.
Q8. Will USCIS waive the filing fees for provisional unlawful presence waiver applications?
A8. No. Fee waivers generally are available only if the fees for the underlying application are waivable. Currently, fee waivers are not allowed for the Form I-130, Petition for Alien Relative, which is the basis for the provisional unlawful presence waiver. USCIS, therefore, will not accept fee waiver requests for the Form I-601A, Application for Provisional Unlawful Presence Waiver. The provisional waiver application fee is $585.00 and the biometrics fee of $85.00.
714-560-0040. The answer provided is general in nature and because not all facts are known, it should not be construed as legal advice. The answer does not create an attorney/client relationship.
I agree. There isn't a fee waiver in this situation. It is also necessary to show that the applicant/beneficiary will not be a financial burden on the U.S. government and requesting a fee waiver may work against your overall case.