The heuristic is that pretty much anyone who is trying to sell you something is out to screw you. They are probably lying, and they are probably trying to get a quick buck from people who don't know better. And when I say anyone, I mean anyone. Youtubers, anyone on TikTok who links anything, advertisements on the web, billboards.
It's not 100% but if you follow the heuristic you save a lot of money and generally have higher quality goods in your life.
The reason we got into this mess is because advertising on the internet broke all the rules. Now lying is de-facto allowed. So then everyone else followed suit to compete. If your competitors are lying, you cannot afford not to lie.
So now all advertisement and sales are compromised and should not be trusted. Even large, previously trusted corporations are running scams in America. Professionals making six figures are acting as con artists. It's unbelievable how fast the situation has deteriorated.