larry - I think you raise an interesting point. I'm not sure I know enough to address it and its validity.
I will make one small point. But first our story. Our 04 son started with a local/regional showcase. He did well...got some interest from a local mid-level D1 school. He then tried a "more regional" (i.e. West Coast) tournament. He did well again and was then invited to a national showcase based on that. There, he did extremely well. From that many doors opened suddenly, including the door to the local D1 national powerhose school.
Point is...I'm not totally sure that the local powerhouse (15 minutes away) really noticed until he performed at the national showcase half a country away. Maybe they just wanted to see him against the best...I don't know? And I don't know that WE even knew how good he was until that national showcase. I just assumed there were many out there just as good or better.
Is this the path that others must take? No, clearly not. But it was a path that worked for him.
I'm often asked by parents now if their son is "good enough" to go to a showcase or play college ball. I answer that I don't know (which is true) even if I have doubts and I encourage them to "take their best shot." Thats what we did and it worked. Everyone deserves a shot and if it doesn't work, well then you gave it a try. Showcases are one way to gauge yourself that is better than most other venues. Just have a feedback loop (engineer-speak) and listen to the feedback and adjust what you do next...which may be to save your money and not attend any more of them.