I was approached by people trying to get me into a pyramid scheme at least thrice in my life. One was a friend who got into it in high school and said I could

I was approached by people trying to get me into a pyramid scheme at least thrice in my life. One was a friend who got into it in high school and said I could get in on it too for 100 USD (~2004). Another was a random stranger I struck up a conversation with at a bookstore in around 2011. The last was an old boss, who attributes his drastic weight loss to a strange drug that he's peddling and says I can get in on. It's crazy. I was 17, 24 and 37 and all 3 times I knew there was something super suspicious about these and never engaged.