Nobody gets free money.
Lets just get that out of the way so we can understand resources and creation of resources.
With harvesting you do give money, yet harvesting costs no computer resources to yourself, other than downloading nano wallet and checking it every now and then.
To me harvesting is a nice little side benefit, some weeks you might harvest .5 xem, some weeks you might not harvest anything and some weeks you might get lucky and harvest 20 or 30 xem in one block.
You do not just plug in and get a lot of cash from harvesting especially around 10- 30k xem, any coin that guarantees large returns from dividends is a scam.
Crypto is a representation of real world transactions, it does not make money out of thin air, any coin that claims to do this is most probably a short lived endevour.