Why do authors need to pay an article publishing fee in Frontiers?

Open access is free for any reader, but it is not free for publishers. Frontiers operates on an author- pay/reader-free model, also known as “Gold Open Access.” Author fees help offset the cost of managing large editorial boards, administering peer review of articles, developing and maintaining the IT required to maintain the journals and the journal website, and many other associated costs. To read more about open access, please see here: http://www.frontiersin.org/about/PublishingFees.