It varies from publisher to publisher, but in most cases information on article processing charges will be either in the submission guidelines or on a separate page devoted to open access fees. Publishers ought to make fees visible to authors in advance of submission so that they fully understand what their obligations are if their article is accepted and what other options might be available, like fee waivers. The conditions for waiving fees should be clear and the process for applying for a waiver straightforward.
—MIT Press, March 2025
Also of interest: What are the open access options for my journal article?