“APCs are waived for authors from developing countries that APS offers free online access to under the SRKS Program.”: https://journals.aps.org/pra/authors#pubcharges

“submission in some electronic formats qualifies for a publication charge discount (Physical Review Letters) or waiver (Physical Review A, B, C, D, E, Applied, Fluids). Acceptable formats for the discount or waiver are currently REVTeX (preferred), LaTeX, Harvmac, or MSWord”: https://journals.aps.org/pre/authors/submission-faq#discount