No, I absolutely would not pay for entertainment on board a ship.
This has nothing to do with my ability to pay, or my budget for the cruise. I find the question, "would it kill you to pay?", VERY offensive. Whether it would "kill me" to pay or not is totally irrelevant.
My understanding of the deal you make with the cruiseline when you book a cruise is that you are buying a room (for the duration of the cruise) with all food and entertainment included.
I wouldn't pay even $1 for food, when I can get very good food that is included in my cruise fare. Likewise, I wouldn't pay even $1 for entertainment, either. I find it mind-boggling that anybody would.
Now, paying a premium fee for reserving the best seats in the house, well, I wouldn't do that for most shows, but I could understand why someone might do that. But that's only okay in my book if the rest of the seats are still included with cruise fare.
Now, on land, they do charge entrance for various entertainments, but that's totally different. WHY is that different? BECAUSE, we are not paying an admission fee that supposedly entitles us to this stuff already. If I go to the movie theater or the opera, why, that's not somehow "included" in my rent or mortgage, and I don't expect it to be free.
In summary, I pay my cruise fare expecting to have pre-paid for all food and entertainment on board the ship. I find it a slap in the face to be asked to pay again. Therefore, I would not pay it.