yes the fact is like that, in this crypto industry there is no full guarantee for you. Even in traditional investment, nothing guarantees you profit. There will be no certainty in future income, and if a project claims their tokens will become more and more expensive over time, it is very likely that they are lying. Of course, that does not mean that they are wrong, however, ensuring that everyone in the inevitable benefit is not responsible, to say the least. If you see a project that claims that your profits will grow tenfold in just six months, it's far more likely to be a good old Ponzi scheme than it really is, as seen in BitConnect.
So, no matter how this promise actually looks, if you see that the project offers you sky-high profits for literally no effort, it probably means that they want to make that profit out of you.
There are promises a project will give and one can tag then scam right away, just like you pointed out, a project saying their coin will worth very high within a very short time is only but trying to lure people in, because everyone knows that new projects first struggles in the initial stage and with constant improvement and depending on the team can achieve their goals but when a new projects starts making unnecessary promise it's good to look twice. Also, any project offering a certain assurance of your investment growing massively within the short period just like the cases of Ponzi should be ignored because it is not far from Ponzi as well.