That's a pretty stunning difference. Please go back and make sure that each and every element of the compared trips are the same.
Get all the way through, both ways, to the point where you kow you are at the TOTAL, not the pre-tax subtotal.
Check the tickets, make sure they are exactly the same.
Drop the insurance.
Make sure the head count is exactly the same, with the same ages.
Make sure it's the same sort of room!
Make sure they haven't thrown Dining into the package.
Just go through and make 100% sure you're comparing apples to apples (and then make sure they are both the same type of apple, and then make sure you're not looking at one conventional and one organic, LOL). Because that's a pretty massive difference.
But if you haven't done so already, check out places like undercovertourist.com for tickets. They are a bonafide discount ticket company. When comparing their prices to Disney, note that Disney doesn't show taxes until you go to look at the shopping cart. If you wish to use UCT, sign up for their e-newsletter. It comes out on the 15th, and includes a link that will give you a small extra discount on top of their normal discount.