To put it simply, the issue with Mark's proposal is that it assumes that owners of future groups will be prepared to pay for their members - a minimum of $0.55 per year, per member .
We shall see... I know that, unless I was getting a larger amount - somehow - from them, I would not be.
Which follows from the basic trilemma of any service like Groups.io: who pays: group owners, group members or a third party (e.g. advertisers). Mark has ruled out (strongly) the last; and (so far, as direct payers) members...
note  unless they are restricting themselves to a small basic group (which again, absent a special need, is not something I would do.