Most online journals ask for payment for publishing research/review articles, under the pretext that no one is making money in the process. Is it really so.
Online journals, and mostly OA journals are asking for money for processing the paper, and in return the author is left with the publishing rights,and he is free to use the paper further as he likes, Your comment could be correct if the journal is not refereed.
In my opinion the best preservation of knowledge is in print format. Today there are many ways to preserve information in digital format (JStore or Muse projects) or preserving it in a cloud, nevertheless, the digital format is not so reliable for preservation since it keeps developing and changing all the time. I have diskettes with a lot of information that I did not have time to convert into disks or disk -on -key, and today the computers do not have diskettes drive. So, this information is lost.