Professors and researchers should start charging for time spent helping the closed journals at the very least.

If you think your reviews are valuable, charge accordingly. You provide value to the publishing process and should capture that value. You are providing the service of "expertise". If you provided that service to a lawyer, you would earn several hundred dollars an hour.

There's probably a business opportunity in creating a clearinghouse for reviewers, editors, etc. and managing the accounting.

Edit: Grammaring more goodly