Nothing really to be argued. They are offering a product people want at a price that people want, and in that regard they are absolutely justified to raise prices. They've been rewarded for those price increases every single time they have done them. Since the prices tend to only go up, remember that this is the cheapest it will be for years to come.
On the bigger scale though, I think the park has been underpriced for a long time. I also think that certain cutbacks that have happened, literally over the course of 20 to 30 years now have mostly been facilitated because the audience has demanded cheaper and cheaper prices for admission. If the audience values money over everything else, they will pay any price for admission and accept any level of quality *just to be there*. I'd like to think that things are going to change over the next few years, as Disney is signaling that they want to elevate their product offerings, but if they don't change, it will be because the audience demanded it.