Unlike you I am not a grant holder and so I have to either beg the public for server costs every month and I'm not getting paid to write or maintain the code. That plus other unanticipated costs, means I have to shell out ~$1k+ a year just to keep the service running plus backups etc. Its a steep cost and I'm also unlikely to ever get a grant fwiw.
So any amount of subsizing is good, if the public doesn't want to donate then its paywall time and if the paywall doesn't cover then its time to move on and either sell the project or work on more substantive work that has more impact for my spare ~10 hrs a week.
not every dev is going to get subsidized, meanwhile plebs are constantly using a service like crazy and demanding it be FREE FREE FREE.... at some point its not worth the tax write off anymore (too steep a cost).