I've heard about cashback systems in casinos - they say they return part of what you've lost. But I've seen more than once that it's pure deception: they give pennies or don't credit at all. Does anyone have experience playing where cashback really works?

https://parimatch-online.in/betting has an honest cashback. Every week you get a percentage of your lost bets, and this money can really be used without complicated conditions. I get from 5% to 10% - it depends on my activity. It's especially nice when you're unlucky for a week - at least part of it comes back. These funds can be used in the game or withdrawn. This is not marketing, but a really working function.