I had a local 4.5 league years ago that had 16 players in it. The winner of each group of 8 played in a final. I won my half and played a 3.5 hour match where I lost 6-4 in the 3rd set. My opponent won a $150 gift certificate and I got a $50. It was the largest prize I had ever played for.
It was worth it though because I found another good person to play and we became good friends. Our boys are the same age so maybe they will be battling on the court soon. His son is way more into tennis than mine though.