My husband has rented tuxes from the cruise line several times. The price that is quoted includes all the formal nights. If you have two formal nights, the outfit will come with two
The tux will arrive in your cabin usually on the first day of the cruise and they will pick it toward the end of the cruise.
Also, if you have any problems with the tux (for instance one time the cuffs on the shirt were very frayed), they will replace the item if they have extras available.
It's a handy service and easier than toting a tux from home!