Tennis Balls For Thought

I hadn't thought about it but this little game has a dark side.  I rarely go to sporting events (usually just when it's work related with Girl Scouts) so when my friend who is more of a regular than I commented on his dislike of this particular activity - not just once but several times - I started to think about the money. How much is spent by regular people in hopes of a great return?  It sounds like gambling and it has started to bother me a little, too.  Hmmmmm ... food (or tennis balls) for thought!