DIVA,
While I certainly can't speak to your situation specifically, I agree with Eck...it is SO unusual for a baseball coach to sit the best players on his team and play "favorites" who's parents contributed time and money....
I can certainly think of times when I've tried to get a backup player in because he's a great kid who works hard, but I've never done it just because his dad donated a batting cage or whatever....often times, that great kid's parents just happen to be great people too, and therefore they donate their time and money. That doesn't mean that is why their son is playing.
Remember, despite how well you know your son, his coach (assuming he knows what he's doing) is with him every day for many weeks, watching his skills. Perhaps your son, or the other boys who you feel should be starting, are not as good as they used to be, or aren't performing as they need to in practice.
What are your thoughts?
"Swing hard in case you hit something" Gary Ward