To start im on board with what others have stated. The only dose of reality at thirteen is if a kid can’t hit the ball out if the infield on a large field or can’t make a throw across the infield. Even then these problems can be from not growing yet. But given he made the team someone believes he has the potential to succeed.
The reality is every player gets a dose of reality at some point. When it occurs ranges from transitioning to the 60/90 field to a MLBer realizing he can’t compete anymore. When this happens it should be your son’s diappointment, not yours.
You made one statement that really concerns me (for your son). You’re worried about the money spent. If you’re looking for ROI you could end up real disappointed. If you’re trying to help your son be a better ball player, can afford it and your son is having fun it’s money well spent.
I figure in your post you were trying to explain the level of play. But don’t walk around telling people your son plays at some elite level. Just say who he plays for. Let them assume the rest. You don't need to feel pressure about your son producing and put it on your son. He's thirteen. Baseball should be fun. Let him decide when the pressure starts. It will probably be high school when he's a freshman thinking, “Look how big those seniors are.”