Pricing principles used by Scholarly Open Access Publishers :
“The article processing charge (APC) is currently the primary method of funding professionally published Open Access peer reviewed journals. The pricing principles of 77 OA publishers publishing over 1000 journals using APCs were studied and classified. The most commonly used pricing method is a single fixed fee, which can either be the same for all of a publisher’s journals or individually determined for each journal. Fees are usually only levied for publication of accepted papers, but there are some journals that also charge submission fees. Instead of fixed prices many publishers charge by the page or have multi-tiered fees depending on the length of articles. The country of origin of the author can also influence the pricing, in order to facilitate publishing for authors from developing countries.”
URL : http://www.openaccesspublishing.org/apc3/acceptedversion.pdf