This is a good question and the topic comes up on here all the time. A search of this site will yield a wealth of information.
Yes, these are a big source of income for coaches. And they can be recruiting events too.
As your player progresses through the recruiting process, he/you will get an ever increasing number of camp and showcase invites, Baseball Factory and other "national" team tryout invitations, international baseball travel opportunities, etc. Filtering these can be a challenge. Mailing lists get sold all the time...generally that's how the emails start coming.
My 2016 now gets daily email invitations for something.
In the context of recruiting (as opposed to doing something for development, fun or travel or whatever), we viewed attending a camp or showcase or tournament as a time/money decision based upon whether a given event was helpful to each son's recruiting process.
We used to look at the communications from coaches to assess how personalized they were...thinking that might be a better gauge of real interest. No more. 2016 has gotten way more "personalized" communications from coaches that are really just camp/showcase invites than my 2012 ever did. And the school has no interest in 2016. But the coaches have gotten more sophisticated in personalizing the message.