Yes you are right. If you reason strictly mathematically, most of the money is spent inefficiently. I mean money for advertising. Since now advertising carries a function not to convey information but to "shout over" the advertisement of a competitor.
Here everything is quite logical. For the attention of investors you have to pay. Who pays the more he gets it. It's bad that the participant of this "auction" who spent certain funds can not get any conversion at all.
The fact is that there are some minimum values of the sums of money that when investing in advertising can give a conversion. The main thing is to guess these values and make the right decision - if money is not enough, then do not start a campaign that will be known to be losing.