The question is a little bit too general, the truth is that internet marketing is not that much different than marketing in the real world, the differences come from the fact you are using a different medium in order to advertise, but the very same principles apply to it.
Question is not general at all, he is asking is it true that "money invested in marketing is equal to profit you make after". I think answer is true, there is examples out there like coca cola, nike, Adidas, do you know how much money they invest in marketing? And not just them, take a look how much money marketing industry make each year.
For many types of businesses marketing is very important part, but there is exceptions. It`s like that in real world, on internet without marketing you can`t do much so here without good promotions and marketing you wont be seen, that is equal to zero profit.