Ok, since my son is a soph and we're at the stage of trying to figure this question out for ourselves, I'll take a stab at this one.
The goal of the showcase circuit is to provide exposure and hopefully more opportunities and greater options for the next level (or so I tell my wife when I hand her the bills afterward). My take is if you're assessed (by yourself or others) as state-wide or regional talent, then local showcases combined with smart target marketing to specific appropriate level college camps should achieve a cost effective return on your investment. However, if your talent is national in scope then the big buck spending on the big national PG showcases makes some sense. JFK in assessing political ascendency said, "If you look up and there's blue sky, go for it." That advice could also work for parents trying to figure out what showcaes fit their son's talent level.
The state-wide, regional vs. national differentiation is based on looking at the rosters of the various D1 programs across the country. The vast majority have an in-state or regional bias. Therefore if you have some talent the local schools are going to know you very well and national exposure type showcases are not necessary in most cases. However some top schools do recruit nationally and if you have that level of talent it would make sense to get on that radar screen too.
I don't equate the national PG tournaments with showcases however. I believe strongly in competing against the best competition so the investments in East Cobb, Jupiter, etc while maybe not always necessary, are always good ones imo (and enjoyable too).
Of course there is always the niche-market to consider; the academic showcases that bring in the top D1-D3 academic schools. I've heard good things about some of these showcases so for the right student-athlete, these showcases have a good ROI too.
ps. I do agree with luvthisgame and Pedro A. that there's a species of baseball players who are showcase-centric. The "tools" (showcase) vs "performance" (games) mindset has the the potential of turning the high school game into an AAU-basketball mindset. Not good. Witnessing it first hand, I call it prima-donna baseball.