With my little experience so far, I have come to realize that most crypto projects that promise Investors excessive returns on their Investment eventually turn out to be scam.
I once participated in a a certain project that was giving Investors about 5 times (5×) bonus during their presale. The team kept postponing the exchange listing date until everybody got tired of them and realized that, it was a scam project.
This really often happens. Many investors are trapped with the high bonus of pre-sale with under price. However, many kinds of those projects are as you said. Moreover, even if they are listing their tokens, they are living in a small exchange or even in a non-trusted and reputable exchange. Additionally, some of the projects always postpone the time for listing and end to be never listed in any exchange. The developers then run away and leave the investors. This always happens but there are still many people who become the victims. Commonly, projects that promise big things too good to be true will always end as scams.