I agree with you. Just speaking to the big 3, I've done the math too. It can be much cheaper to sail with NCL if you actually want drink and dining packages. What really sends them over the top for us is airfare. We live in KS (not KC area) and can't touch their 2 for 1 fares. It's not really 2 for 1 sometimes, but it's still hundreds cheaper than I can book it for myself. Sure, I give up control, but I save so much it pays for the free at sea gratuities and then some. We can, and have, driven to Galveston, but the itinerary's are limited. I want to go more places.
You really have to know what kind of cruiser you are to compare. If you like all inclusive and paying for everything upfront, NCL is the way to go. If you can drive to a port, don't drink or drink very little, don't necessarily care about specialty dining, the others can be much cheaper. That doesn't mean cheaper is better for you. If you don't drink, Carnival's party hearty atmosphere is probably not for you. If you don't like Cirque, RCL's entertainment may not be for you. If you don't like Broadway shows, NCL's entertainment may not be for you. There is a line out there for everybody, and some people enjoy them all, but you have to know what you like/need to pick one. That's the key. And that's only the basics. I won't even try to get into the whole upgraded experiences like Haven. It's a lot to process if you haven't cruised before.