One reason why the Allure and the Oasis are costing more is because RCCL raised the NCF's (non-commissionable fees, also referred to as port fees).
Some people may not know this, but the price you see advertised is actually the total of two fares; the cruise fare and the NCF's. The NCF's are a total of the port fees they cruise line is charged based on the number of people on the ship. In other words, it's a 'per person' fee. Cruise lines will not release how they come up with these fees and they always seem to change without any reason as a way for the cruise line to collect more money from the passengers without increasing the cruise fare, which would increase their commission payment to agents.
As I mentioned, this is a 'per person' fee. Yet when traveling single, some cruise lines will double the cruise fare and double the port fees, which is not appropriate. Some cruise lines will charge double the cruise fare and single the port fees, which is appropriate. Strange thing is, NCL will charge single the port fees if traveling in a single cabin, but double the port fees if a single is traveling in a double cabin!
I could go into it further, but I think you get the picture. But the reason I point this out is because RCCL has chosen to raise the NCF's on the Oasis and the Allure but not on their other ships. The price of the NCF's went from $159 to $175 on all 7-night Caribbean cruises for all their ships, but now they have raised the NCF's only on the Allure and the Oasis to $275, thus causing a $50 per person increase a few weeks ago.
The thing is that port fees have not gone up, so they're basically charging an extra $50 per person just as way to increase revenue.
And while prices on these ships are higher simply because of supply and demand, it helps explain one reason why the prices for the Oasis & Allure are higher now than they were.