Nowhere in my contract or in anyone else's contract (as far as I know) it is written that I need to referee papers.
People do it as a service to the community. And I don't necessarily ask to be payed for that, I was just answering the point about "I want everything to be free all the time and never pay for anything". We pay with our work to referee the papers. Sure there are extra costs to host the papers, typeset, but they should be nowhere near 2.5k GBP per paper.