Wow, that is awful. I wouldn't have believed that was possible, but I just checked thier website and the very first entry under Terms and Conditions reads:
All rates are subject to change until package is paid in full. After package is paid in full, rate is subject to change due to imposition of taxes or other charges of governmental authorities. All rates are in U.S. dollars.
Considering that airfares fluctuate more than the stock market, I'd say if the money is readily available (or available at a low interest rate), you should pay the whole thing off immediately. Unless you want to risk it rising even higher. (I'm no airfare genius, but my experience has been that once it goes up, it doesn't come back down very much.)
The other option would be to cancel the whole thing and start over. I'm pretty sure that you don't save any money buying a package from WDW. If you buy all the pieces separately, you can save money by shopping around for the best airfare and getting discounts on your room. If your trip is the first or second week in December, I think its safe to assume that you'll be able to get some sort of room discount, even if it is only a
AAA 10% discount. The only disadvantages to this is it takes some legwork on your part and you'd have to pay for your airfare in full when you book it - that could be a problem if you don't have all the money right now.
