And that's what is skewing the numbers for you.......its an expensive day. Some of DC's inclusions (for which you are paying in the per person rate) are 14 days admission to both SeaWorld and Aquatica. If you choose not to use the inclusions for which you are paying, then certainly the balance does seem costly.
Your best value is doing Discovery Cove on a SeaWorld/Aquatica/Busch Gardens trip. And quite honestly.......if you are looking at what else you could do with dollars saved, you would save a PILE by doing a SW-based trip as opposed to Disney.
Our SW-based trip over Christmas was half the cost (for room, tickets and food) than what we would have paid at Disney. I priced it out before booking. And I'm not knocking Disney here.......but if you are comparing "hey, DC is expensive when compared to Disney" then its fair to compare other angles. You could easily do a SW trip in larger, more inclusive accomodations (having extras such as a daily breakfast buffet and free front of the line passes) with tickets and save enough to pay for a day at DC.
If you add a single day at Disney when doing a SW trip, its ridiculously expensive. Your family of five would be almost $500 just to walk in the gate for one day at at Disney park, if admission was purchased as a stand alone. That's no food, no parking, no drinks, no souvenir photo, no extras of any kind. The same would be true if you decided to do just one day at Universal.
I hope you are able to get a deal on Discovery Cove admission. It really is a wonderful place like none other in Orlando.