Stephen Pinfield, Jennifer Salter, and Peter A. Bath have published "A 'Gold-Centric' Implementation of Open Access: Hybrid Journals, the 'Total Cost Of Publication,' and Policy Development in the UK and Beyond" in the Journal of the Association for Information Science and Technology.
Here's an excerpt:
This paper reports analysis of data from higher education institutions in the UK on their experience of the open-access (OA) publishing market working within a policy environment favoring "Gold" OA (OA publishing in journals). It models the "total cost of publication"—comprising costs of journal subscriptions, OA article-processing charges (APCs), and new administrative costs—for a sample of 24 institutions. APCs are shown to constitute 12% of the "total cost of publication," APC administration, 1%, and subscriptions, 87% (for a sample of seven publishers). APC expenditure in institutions rose between 2012 and 2014 at the same time as rising subscription costs.