“the total time reviewers globally worked on peer reviews was over 100 million hours in 2020…The estimated monetary value of the time US-based reviewers spent on reviews was over 1.5 billion USD in 2020”
The authors of the paper above published on “Research Integrity and Peer Review” have assumed that on average a paper takes 6 hours to review. More interesting however are the numbers that they presented in Table 1 and were used to calculate the reviewer´s hourly wages in US ($69), UK ($57), and China ($33).
On this subject check also a list of 28 European countries ordered by the ratio (number of reviewers with more than 400 confirmed revisions of papers from journals indexed in Web of Science)/(million inhabitants) that show researchers from Germany and France do not like to make time donations.
PS – Let´s also not forget the article on the rise of “dodgy academic journals” and how citations can be used to spot those journals https://pacheco-torgal.blogspot.com/2020/06/the-economistin-just-20-years-predatory.html