The first showcase my son attended was a non invitational local showcase. Sure some invites were sent out but if they dont know who you are that's not going to happen. On the web site they listed the colleges that have attended in the past. I would say that the majority of the players were marginal. My son did hear from many colleges after the event.
The second showcase we attended was a newer organization from the west coast-they held a few east coast showcases last year and again there were not a lot of coaches in attendance. Out of 120 kids there may have been 10 D1 players there. 3 kids from that showcase were asked to go to Marrietta Ga. to the PG/WWBA Tournament-my son was 1 of them-needless to say the exposure there was awesome.
My point is that if you can play but they dont know who you are- or if more expensive showcases and travel are a concern- even a smaller showcase can be benefical.
IMO PG is the biggest bang for your buck- we kind of took the long road there- but eventually we found our way there and it paid off.