Disney allows you to book a room as a Guaranty. Which means that you don't pick a cabin number. In return for your willingness to be placed where ever
DCL needs to place you, you have the possibility of being upgraded to a better cabin. A good bet is booking a cabin at the Cat 12GTY level and then hope for an upgrade to something much better. That way you get a great cabin at a great price. Of course, you need to be happy with a cat 12 if you end up there.