Yep I agree the Disney wish book isn't perfect but it can give you a basic idea of how much money is involved and what the options are....
My DD is having her DFTW on 1/4/2008....at first we had thought she would get married in her home town, but after she really couldn't find anything that she really wanted, I asked her about her earlier wish to get married at WDW....once we started investigating, the amount of money that we planned to spend turned out about the same....the only difference being the number of guests (fewer)....
DH and I are excited about our daughter's wedding and know that every penny will be worth it....we are Disney lover's through and through and this is a once in a lifetime experience!.
I would say you could spend anywhere from 7000.00 to the sky's the limit....(Katie's is running approximately 23,000....)
Good luck to you guys - the planning process is exciting