Page charge payment

I am writing on behalf of Acta Biochimica Polonica editor, Polish Biochemical
Society. We are working on the implementation of OJS for our journal and we have
found tiny but painful problem: we charge our authors per page (plus additional
fee per color page), not just a submission. Have you ever met such policy? I
believe it is quite common in open access community.

This is not currently supported in OJS, but @jprk may be working on something similar: