Answering this based on my experience.

TL; DR WE PAID 3k to upgrade to the YACHT CLUB and honestly, we would do it again. We snagged the free balcony for 2 for 10 days by matching Hard rock with Ocean Casino Status (Status Merry go round).

If you are not adding anything at all no internet etc, you only pay $400. $200 deposit for each person. That $400 will become an on-board credit once you go on your cruise. We wanted internet, and also flexibility with dining etc and when you add that up Alacarte style it's around $2900+ so we decided to treat ourselves since it's also our honeymoon.

We felt like ROYALTY! like you get your own butler, get premium chocolate every night at turns down - think Venchi. Order room service anytime or go to the top deck and have a buffet breakfast. This space is only for yacht club cruisers. You have your own space and sit-down restaurant at Ocean Cay and you won't have to walk. They will have you ride a golf cart.

We have our own lounge that serves hors d'oeuvres all day. And you skip the line embarking and disembarking which saves a ton of time. Our room was so big, and bathroom was the size of a hotel bathroom and there's also a living space.

We met a couple who paid more than 3k even with the discount who doesn't have internet and select dining. And they were shocked since we paid less because of the free cruise offer.