I presume your son is talking specifically about D1 recruiting? If so, he would be pretty accurate. At least in SoCal, it is really about the level of travel team a kid plays for (unless they play for a really strong HS program). And those kids on those teams who are playing in the bigger recruiting events really don't need to go to showcases because they are seen. Many even get invited to specific weekend showcases at certain P5 schools that give them even closer exposure.
But for the kids who are not D1 (which are the majority of HS players seeking to play in college), must of them have to go to more events, including the big showcases, to be seen by the coaches in their pool-D2, D3, NAIA and JuCo. And it helps to have PG, PBR and/or BF provide measurables from one of their events to be able to send to coaches in recruiting e-mails. Unfortunately these things do cost money, but if they did not provide some results, they would not survive. Sure, they may be "money grabs" from some kids who have little to no chance of playing college baseball, but at least the parent(s) and kid can say they gave it a shot by spending the money, and then seeing no interest, face reality.
I've always wondered how many kids miss out on a chance to play college baseball because they mistakenly believed that the colleges/coaches would find them. Yes, elite talent is found without much recruiting work on the kids end, but the lower divisions have limited funds to see recruits and the showcase events are the most effective way for them to find their potential recruits.