ERROR offers reviewers a base fee of 250 to 1000 Swiss francs (roughly $300 to $1200), and bonuses of up to 2500 francs if they spot errors, depending on their severity.
The project planned to carry out 100 in-depth critiques in 4 years, but only nine have been completed so far, with eight more in the works. Candidate reviewers identified by ERROR often decline requests immediately, agree to do the work but don’t follow up, or ghost the project organizers after a few emails, Elson says.
https://www.science.org/content/article/offering-scientists-cash-spot-errors-published-papers-doesn-t-work