I'm having the same problem for our family of four; it will be over $700, so not quite as much, because DH and younger DD don't care to swim with the dolphins. The only things I've been able to come up with are:
1) Swimming with dolphins is one of the things on my list of "things to do before I die".
2) The dolphin swim is my birthday present for my birthday this month and my oldest daughter's 19th birthday present for her b'day in July.
3) We get to come and go at Sea World for seven days, included in the price, as well as a good lunch, so we probably won't go out to eat that particular evening, but just snack in the vacation home we're renting. Sea World doesn't appeal to younger daughter so much, but oldest is very excited about getting to see the penguins, and they are both excited about Kraken. DH could do without it, but he's along for the ride whatever we decide.
4) Our daughters are almost 19 and almost 16. Chances are this is our last visit to Orlando as a family because we want to take a cruise next year and go some other places before oldest graduates from college and goes out on her own. So if we're going to do it, now's the time.
I may or may not have given you anything to think about, but there you go. I got lucky---our dental insurance company unexpectedly gave us a $730 refund on our younger daughter's orthodontic care after my hubby's company changed insurances. Their policy is to pay regardless of what your former company paid, so I took it as a sign to go to Discovery Cove!!