As a co-owner of a legacy Free group with a lot of members, I am relieved that these new prices won't affect me. I am concerned that they will put off potential new groups and upgrades of old groups.
For me it's a contribution to a low-budget hobby; when looking for a group host site as we moved off Yahoo! Groups two or three years ago, a $3000/year cost for a Premium plan would have ruled out Groups.io completely. (My personal spending on vintage sewing machines, for which I help look after more than one group, is less than $100 per year. Yes, donations might cover some of the costs, but wouldn't arrive until after signing up and paying out first.)
Would it be realistic to charge a per-member cost which decreased with larger groups? For example, less than $0.55/year for members after the 800th for Premium groups?
Of course I appreciate that Mark has to raise the costs of running his business. I also appreciate the excellent system he has created and is maintaining. Thank you!