I have been doing the club thing for a few years now. It does seem it is a common occurrence for clubs to ask you to pony up for an extra tournament. It doesn't happen every year but it happens a lot. I don't think its always done with malicious intent. A few times a tournament we signed up for didn't have enough teams in a certain age group. They signed us up for a different tournament and charged us the difference. If you have an older kid and only get 4 tournaments included in your tuition, assume you will get charged for more. Most clubs do at least 5 and some do even more. Don't be afraid to crunch the numbers and ask how your money is getting spent for the extra tournament. If they give you a hard time for asking, look for another club
