Avira,
you need to be more clear where you quote Sh’A and where you introduce other ideas, because you are not just confusing me, you are confusing yourself. He is not saying “for example, a Rav”. He specifically says – Rav of the City. If someone else says something that you want to rely on, shoin, bring that quote.
I agree though that the quote may not be straightforward. Rema starts with “yesh omrim” and then says “Rav of the City – this is done in all medinos Isroel”. Either, he includes only Ashkenazim in all medinos isroel, unlikely, or Rav of the City is paid everywhere – despite Mehaber’s original shita. And what then does Mehaber mean? So, maybe Rema brings Rav of the City as a proof to demonstrate that there is no absolute prohibition for healthy people. Is the sky the limit? Rema does not say.
But even according why can’t at least some people try to do things an ideal way? If you are inspiring to be a Talmid Chacham, why not try doing an hour a week? Maybe sell esrogim once a year, or peddle your own seforim, like Chofetz Chaim did?
PS I am not consistent here though – I get ads from an ehriche local yeshiva offering free car washes from the students and I do not have a heart to use the service. I’d rather force my own kids.