RCI was forced to take Oasis to Europe for the dry-dock since there are no shipyards in the western hemisphere that can accommodate a ship that large other than Newport News, but those dry-docks are reserved for aircraft carriers. Other options were in Asia.
I am not sure where they will price those transatlantic cruises. Typically they are bargains but this is the Oasis. However, it is also the Oasis in a different way, meaning they have a LOT of berths to fill and that might trump the premium pricing Oasis commands on it's usual cruises.