Gem Spa Day Pass

[Lumee23]

Hi everyone! A large group of us are cruising on the NCL Gem on 1/2/16 for my wedding. I wanted to treat my bridesmaids to a spa day pass but I read somewhere (can't find it now of course) that if enough full cruise spa passes are sold there won't be any day passes available. Is this true and if so does it happen often? I know you can book the full pass in the terminal but at what point can you buy just a day pass? Anybody know how much day passes cost right now? TIA for any help!!

[jjikids]

In May our shipmates were able to book only on the last sea day with a $40 cost per person. They did it but felt it was too much money.