Bruce: You said everything I would have liked to say only BETTER!
What is it with people now days? No matter what, they just can't be please or satisfied. Is no one willing to bend or be flexible anymore? Perhaps the O.P. is right...if their budget is so tight that the lost of 'one' day cruising spoils a WHOLE vacation..then cruising might not be for them. Like any vacation taken at the same time with hundreds or maybe a couple of thousand people, inconveniences can and often WILL happen. I think HAL is doing as much as they reasonably can to compensate passengers. Is it ideal...no, because the ideal would be to have your one lost 'day'...is the compensation reasonable? Yes.
An alternative: Place all three sick passengers, family members or traveling companions in a medium to large dingy with a couple of the crew, food, water a radio and let them sail out to sea (AWAY from the ship of course)for help. This way NO passengers are inconvenience and wouldn't miss any cruise days. Interested passengers could stand on the deck and wave good-by knowing that care is being sought and they can still enjoy their vacation. After all...."It's not our fault they got sick, why should we suffer."
I'm sure the 3 sick passengers and their families are pretty ticked off that their cruise was cut short too.