[yincrash]

The peer review process, I would think.

[Someone1234]

They don't pay for people to peer review as far as I know.

[dragonwriter]

That the individual peer reviewers aren't paid does not imply that coordinating the peer review process is cost-free to the publication.

[infogulch]

Nope, peer review is done by unpaid volunteers as well.

[kansface]

Sure, but they have a layer of editors/reviewers to filter out the bullshit.

[ddebernardy]

Isn't that actually peer-reviewed too?

[gipp]

Peer review has always been on a volunteer basis.