Also cheap is a relative term, generally it costs around $3000 for us to publish in an open access journal!
It's worth pointing out that, according to the Directory of Open Access Journals, most open access journals don't charge processing charges (APCs) According to Heather Morrison, the figure is 26% of journals listed in the DOAJ.
Also, another recent development in the UK is the Higher Education Funding Council for England policy
This policy essentially bypasses the publishers by mandating the 'green' route to OA -- adopted, in various forms, by 3/8 universities in New Zealand so far -- where all published research has to be deposited in an institutional or disciplinary repository.
It's also worth pointing out that 80% of published research could be made openly available for free within a year of publication, if researchers chose to deposit their work in their institutional repository. The fact that only 12% have done so reveals, I think, the need for strong institutional and funder mandates.