I read elsewhere a comment from a mother that she 'Forgot to return her daughter's band' after their trip. Which means they must request them back. Maybe that's why they're expensive, they retain a deposit value? But at the same time that makes no sense because why would you have it at home for Disney infinity if the cruise line want you to hand in before leaving ( ? ).
Just read up... The bands are issued to kids 12 and under to allow free access in and out of the Oceaneer kids club. The coloured 'slider' on the band indicated if the child has a food allergy or not. ( red for yes ). Anyway, the bands are supposed to be returned before you checkout/disembark. If you do not, a charge is added to your bill. This is also why they are so rare as most parents probably aren't aware of the Infinity connection, and don't want to incur more expense at the end of the cruise.
But this seems cheeky to me, because even though you have paid for your cruise ( a pretty penny i would think ), you are then required to cough up more for the band if you want to use it for the Infinity unlocks, or you keep it as a souvenir. They are also encouraging people NOT to return the bands as the band is the ONLY way to get the DI toys. I don't know, is it just another way to generate revenue? Charging you £15 for a £3 wrist strap ( I actually have no idea what they cost ). But I always look at everything cynically. That's just me.