Bonuses are not intended to deceive investors. Giving out bonuses is a strategy adopted by every business not only cryptocurrency projects to boost sales. This is the main reason behind the bonuses projects offer during their token sales. And as the sales get to its close, the bonuses are lifted gradually hence it becomes an early bird catch tactics.
In a case where the bonus becomes extremely too much, it shows to me that the project itself has no value and the project just placed that value on it to be able to easily extract money from investor, and the way they will easily get to investor is to give them high bonuses, yes I agree with you that discounts are a way to help the project easily get to investor on time, but using huge discount when they know that it can easily crashes the market when investors dump it on exchange is a huge scam to me.
Huge scam in the sense that they deliberately did that so that the crash of the project can be accused on dumping and then the developer can exit the market easily, which is why you see most projects crashing and you see the team not even worrying about it at all.