If people want to be included in the weekly points for their division / ctps / Longest puts and such, its 35$. If someones in town and they want to join you for your league round. Bring them out and have them play a round with ya. They just are not eligible for the Ace pool/ CTPs/ LP or points from the league as that's all end of the year stuff.
If you do have extra people playing, to make it easier on the League admins. Please have their scores recorded on another scorecard for them or keep track on there own or what not. Just so Chad doesn't have a score for a player not in the league.