Why pay a reading fee? There are plenty of people on AW and other forums that read for free. Most literary agents don't charge a reading fee, and some actively state that those that do are not the best ones to go for
Violets, they call them 'reading fees' but it's not for beta reading or critiquing, it's a cost for submitting your work for publication. I don't know if they're charging for someone's time spent reading submissions, if they're charging for the submissions software, or something else. One journal I looked at said it was for printing and making copies for their editors, and didn't charge if you submitted hard copy via snail mail.
Honestly, it seems to me that those things are operating costs that should be covered by revenues from subscriptions, advertising, etc., and should not be passed on to prospective authors.
Of course, it could be that their trying to discourage or slow down submissions. Some journals are buried in material.