Alternatively hear me out you could have people who actually care about other people make a website that treats people like they want to be treated charges a modest per month fee to users looking to do a good job and turn a profit. Unless you've already signed a deal with the devil with people who don't give a fuck about other people it doesn't have to be a maximal profit per user it just needs to be more than the cost to run the site.

If you don't constantly redesign your site or feel compelled to use the most expensive hosting possible, or cosplay as google it doesn't even have to be that expensive. A single actual physical computer could serve a hell of a lot of people for a modest amount of money. The $20 OK cupid charges per user could trivially pay for the oh so complicated task of allowing people to find and message like minded users.

A doctor doesn't need to work around the market economics of not making people sick so you can cure them they have agency they can choose just to be a good doctor and most of them do.

I think many of the dating sites started that way. That's why they were better in the beginning. But eventually, they go public, or get acquired, and end up getting run by people who are bottom line focused.

People are avoiding marriage these days and experimenting with noncontractual arrangements like polyamory. Even before the fraud materializes, the proposed system would be a total failure based on societal changes.

Always get paid upfront. Net-anything just gives others time to find a way to cheat you.

I think 40-60% of people are still seeking escalator-style relationships that would result in marriage (even if they're not seeking such relationships immediately), which is an enormous number of people