We booked on board in May, and YES you do have to pay $250 a person deposit, in our case $1,000. She asked me if I wanted to put it on the credit card I had secured at guest services, and I said yes, so it was all done without even opening up my wallet. You don't see it on your bill you get from guest services at the end of your cruise. You see it on your credit card statement you get in the mail, the following month. The on board booking quirk is a $200 on board stateroom credit, for your next cruise.
Joanna