I actually did that dive 2 years ago. It was $200 then, as well. I viewed it as a contribution to the Ocean Centre and not a fee.
I was quite impressed with how they run their aquarium. All the water is pumped from the sea and returned. Much of the exhibits are in recuperation states. I find it more directed to the actual portrayal of sea life than entertainment. You won't see any jumping dolphin acts there. I was more than willing to make that contribution.
It is a fairly long day for a short dive. There is a mandatory briefing that takes some time.
The dive was amazing. The day we were there was special, the tiger came down and was circling at mid tank (that's what I get for wearing my seal-flavoured wetsuit). Miss Piggy was picky that day and not hungry, but kept pretending she was. The sharks and rays weren't that interested in us, but it was pretty life changing to be in amongst that number of them.
Seeing the faces of the kids through the glass was almost as much fun as the dive. The aquarium is open to the public at that time, so you're part of the exhibit.
You do get "backstage" passes to the aquarium for the day, so you can see some parts that the public doesn't see (star fish breeding tanks, etc).
For me (from the prairies), it was well worth it and a good change-up. I saw it as more of a once-in-a-lifetime thing and it was definitely something I will remember for all time. I was lucky enough to be in the water and see (and film) a humpback and her baby up close that week as well. It was indeed a special week.