IOP Publishing offers authors discounted OA publishing across all its journals - IOP Publishing

"Researchers from countries with lower-middle income economies, as categorised by the World Bank, can now choose open access (OA) publishing in any of IOP Publishing’s (IOPP) journals for a flat charge of £500. The policy builds on IOPP’s existing approach that enables researchers from countries with low-income economies to publish OA for free in any of IOPP’s fully OA or hybrid OA journals.  IOPP’s decision to extend its Article Publication Charge (APC) discount policy to authors from countries with lower-middle economies acknowledges the importance of author choice. It is another step toward greater inclusivity for researchers who might otherwise not be able to contribute to the global body of openly accessible research...."