There are those who demand journal peer-review be paid extra on top of academic salaries. Let’s have a look at the financials of that proposal. The article linked above confirms common rates of academic consulting fees, i.e., anything between US$100 per hour for graduate students and US$350 per hour for faculty. Taking a conservative US$200 as an easy, lower-bound estimate for, say, a post-doc hour seems to cover most cases.