You comparison has to be between ships and the Allure and Oasis are priced quite a bit higher than any of the others. I think this will continue for another year or so but then things will changes.
These two ships are something everyone should do once, but in talking to a lot of clients and friends who have done it (and myself included) there will not be a second time.
When on a ship I want a cruise - that is what I'm hearing. Taking a cruise means seeing the ocean, watching the sky, pulling into the docks. That really doesn't happen on these two ships unless you go out of your way. Way out of your way.
I believe that within 2 years there will be difficulty trying to fill them - certainly at the present pricing. I also believe that same reasoning has to do with why they will be the only 2 RCL ships sailing the Caribbean in the summer months.
However, it is my opinion and I've been wrong before.