There is no charge for entertainment on Royal Caribbean.
I've been on many RC cruises & have never had to pay for entertainment. You are probably confused that the ice show is ticket only. These are FREE but are first come , first served basis. the rest, I suggest, is urban mith.
All entertainment is free on RCI ships. Not sure where you are getting this mis-information from.
The only extras you pay for will be your drinks, your casino, your shore excursions, and if you visit the speciality restaurants. $3.95 for Johnny Rockets, $20 for Portofinos and $25 for Chops. If you don't utilise any of these then you should have a mimimal on board account.