To add to point #1 above, not only are most teachers willing to help out students, but do you really want to be recruiting reviewers who are trying to make $10

To add to point #1 above, not only are most teachers willing to help out students, but do you really want to be recruiting reviewers who are trying to make $10 a pop? My gut feeling would be that people reviewing student work because it means something to them would do better work than those who are in it for a token amount.