$ always gets involved in the secular versions or there's
   complicated channels if one wants to go the free route. Of
   course there's $ involved in religious groups too but the free
   will part is usually pretty important, so it's not required in
   most of them. A secular example: museums. "Suggested Donation".
   Seems like the same idea but it's far more structured: I forget
   which museum it is - I think museum of natural history in NYC. I
   was last there like 20 yrs ago so prices have likely changed.
   Technically, it's free. But just try to get in there for free.
   There were like 15 turnstiles. All pay. There was 1 free
   turnstile. Just try to get through it without being socially
   blocked. Bits of shame along the way up there. People trying to
   redirect you to the pay turnstiles. Maybe it's improved but boy,
   they didn't make it easy.