Rose,
You are right the other cruise lines are much cheaper to Alaska. But you really need to ask yourself what you are getting with the
Disney Cruise.
I just bought my Mom a cruise to Alaska. She said that she was CONSTANTLY bothered to spend money. They had people running by her dinner table trying to sell roses, Incessant waitstaff hawking drinks, Free roomservice? Fugedaboutit, Let's talk stocked refrigerator with overpriced foods and drinks. Speciatly restaurants, yes, but one of them had the EXACT same menu as the cost included restaurant.
Boiled down, she said that she had to work constantly to stay at budget as things that they wanted cost money (not just the cost but the overpricing of objects)
I'm hoping nothing has changed with Disney but my experience was that if I wanted to spend money there was plenty to do so. But in no way would my vacation been diminished if I decided to not spend anything. There was no pressure to spend on the Magic.
Now, not being bothered on my vacation is HUGE in my book. And worth a great deal of money, but besides that I'll bet that after spending what a Disney cruise would have cost you in the other guys and all the extras that you have to buy, you'd come up close to even.
Just my $0.02