Mostly papers are thrown up on arxiv. I don't see why we should have to pay to host our own papers when we could just host our own papers. Seriously, three grand? How many months of AWS S3 does that pay for?
Furthermore, many people just put pre-prints on arxiv etc. and don't update after peer review. Peer review is painful at best and quite flawed but the median paper is actually better after it, and many papers rightly don't make it through. Having open-access curated journals makes a lot of this better.
I am not involved in this stuff, just read quite some posts on StackExchange Academia.