https://publishingsupport.iopscience.iop.org/questions/article-publication-charge-discount-for-reviewers/
Article publication charge discount for reviewers - IOPscience - Publishing Support
Aug 4, 2023 - To help recognise the vital contribution our reviewers make to the publishing process, IOP Publishing has a reward programme based on open access discounts....
article publication chargefor reviewersdiscountiopsciencepublishing