Here, again, is the Hewlett Foundation definition of OER - "OER are teaching, learning, and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use and re-purposing by others. Open educational resources include full courses, course materials, modules, textbooks, streaming videos, tests, software, and any other tools, materials, or techniques used to support access to knowledge." 
The essential part of that definition is that they have 'an intellectual property license that permits their free use and re-purposing by others.' That's how the quality gets kept up to date without the need to pay publishers to pay teachers and professors to update the curriculum. Publishers don't have a secret group of magic wizards locked away in a book shelf lined room somewhere that do the editing of the content that publishers use to extract huge sums of money from cash starved public school districts. The real 'secret'- publishers hire K12 teachers, and retired K12 teachers, and higher ed professors, and professors who used to teach in higher ed, and PhDs who hope to teach in higher ed to do the editing and revising. Of course, the publishers are going to say that we need them, the publishers, to organize that rascally group of editors and revisers, and that was sorta true back in the 20th Century and before. Not so today.
Yesterday, in a piece entitled New Open Ed. Group Vows to Battle Commercial Publishers for K-12 Contracts Sean Cavanagh said that Open Up Resources is going to pay for the editing and revising of their OER content by offering professional development to K-12 systems; printing and distribution services; and support and maintenance for districts seeking to use digital versions of the open materials. That's a solid plan. Open Up Resources will have even more chance for success if they encourage K12 teachers to collaborate with the higher ed professors at their higher ed teacher prep institutions - the people they've relied on for a century or so to prepare, certify, and re-certify teachers. I talked about that in this post. I haven't heard any objections to this idea in recent meetings with U.S. Dept of Ed officials and administrators of higher ed institutions. There's been a little chin rubbing about how to make that happen, but there's also been lights going on.