Many estimates have been made of the true costs of Gold Open Access (OA) publishing (e.g., by Claudio Aspesi, in the discussion of
Richard Poynder's recent article), but the estimates are rather arbitrary and unrealistic if the other causal factors that could raise or lower them are not taken into account.
The two most important causal factors are (1) Green OA and (2) institutions' subscription budgets.
Institutions cannot cancel essential journals if their contents are not otherwise accessible to their users.
If Green OA is universally mandated, then authors' final, peer-reviewed drafts of all journal articles are deposited in institutional repositories and freely accessible to all users whose institutions cannot afford subscriptions to the journals in which they appeared.
This makes it possible for institutions to cancel subscriptions, eventually making the subscription model unsustainable as the means of covering the costs of publication.
Subscription cancelations force journals to cut inessential costs.
With the refereed final drafts of all articles accessible to all through Green OA, journals no longer need to (1) provide the print edition, (2) provide the online edition or (3) provide access or archiving: The distributed network of Green OA repositories provides all that is needed. The rest are all obsolete products and services in the universally mandated Green OA era.
When the costs of (1), (2), and (3) are unbundled from publication products and services made obsolete by universal Green OA, the only essential cost remaining is that of implementing peer review.
Peers review for free, so the cost of peer review is just the cost of managing the peer review process, including the editorial expertise and judgment in choosing referees, adjudicating referee reports, and adjudicating revised drafts.
If peer review is provided as a "no fault" service to the author's institution, per submitted draft, regardless of whether the outcome is rejection, revision, or acceptance, the cost of rejected articles can be unbundled from the cost of accepted articles; this not only lowers and distributes the cost of peer review, but it removes the risk of lowered peer review standards and over-acceptance for the sake of making more money through Gold OA.
This much lower cost of post-Green OA no-fault Gold OA -- my guess is that it would be between $200 and $500 per submitted draft -- would not only be incomparably more affordable than today's pre-Green OA fees for Gold OA, but the money to pay for it would be available, many times over, from a fraction of institutions' permanent annual windfall subscription savings released by the cancelations made possible by universally mandated Green OA.
The only essential element for having Gold OA at this much more realistic and affordable price is one cost-free act on the part of the universal providers of all research output: Institutional Green OA mandates (reinforced by research funder Green OA mandates).
Without taking these costs and causal factors into account, estimates of the costs of OA are arbitrary and the wait for universal OA will continue to be long.
Harnad, S. (2007) The Green Road to Open Access: A Leveraged Transition. In: Anna Gacs. The Culture of Periodicals from the Perspective of the Electronic Age. L'Harmattan. 99-106.
Harnad, S. (2010) No-Fault Peer Review Charges: The Price of Selectivity Need Not Be Access Denied or Delayed. D-Lib Magazine 16 (7/8).
Harnad, S. (2010) The Immediate Practical Implication of the Houghton Report: Provide Green Open Access Now. Prometheus 28 (1). pp. 55-59.
Harnad, S. (2011) Open Access to Research: Changing Researcher Behavior Through University and Funder Mandates. JEDEM Journal of Democracy and Open Government 3 (1): 33-41.