My discipline is conference-heavy; all the copyediting and layout generally falls to assorted grad students and other underlings at whichever institution hosts the particular conference that year.

The major publishers (who need to get involved to have the proceedings indexed and "counted") get everything ready to publish online (well, they do slap a cover on the thing and get an ISBN) after the review process and technical process is done, and still try charge for access to the articles.

> I believe copyediting and layout is paid, however.

I've published in Nature Physics, Physical Review Letters, PRA ... and we did 99% of the copyediting and layout (with LaTeX and unpaid, of course). The editor would correct a few typos, modify the layout slightly (1h of work tops) and that was that.