I think 40% is not high because there are projects where I know the bonus to 100% for early investors, moreover for private buyers, the bonus is much higher. That's the main reason why the listed token's price has dump, Investors should be wary of overly high bonus projects.
Obviously of the early investors get 30% or 40% bonus, then what is the need for them to wait until the ICO is completed? They can just dump their tokens and pocket this 40%. And trust me, 40% returns in one month time is not bad. You don't get such chances very often in the cryptocurrency market. If I was one of the guys who got the 40% bonus, then I'll be dumping the tokens as soon as I can.