I'm in the process of planning my Disney wedding for this April.. you can look at my planning journal on the boards to see the process as I document it! You can start talking with a sales consultant at the 16 month mark, you don't sign your contract until 12 months before the wedding, which is also when you get locked into the prices. Prices have already gone up since I signed my contract this past May. We invited around 50 people (we are only expecting around 35) and are having brunch reception. The biggest way to cut costs by far is by keeping your guest count LOW. For example, the food and beverage minimum for brunch when I signed my contract was $125 per person, not including 24.5% service charge and 6.5% sales tax (I signed my contract in May, so this per person minimum might have gone up by now). Your guest count also affects the number of tables, chairs, linens, etc. you will need to rent.. the less people you have the less tables you will need and the less centerpieces (unless you just have minimum floral and decor)
Also, I think the price of the ceremony venues have gone up.. I paid $4000 for the Wedding Pavilion, but I think it's up to $6000 now. You also have an enhancement minimum depending on the day of the week you get married (mine is $10,000 for a Saturday, again this has probably gone up)
Basically, the minimum I am required to spend is $17K (and some change).. this includes the $4000 Wedding Pavilion fee, the $10k enhancement minimum that can be used towards floral, decor, characters, transportation, photography, etc, and my food and beverage minimum which was only contracted for I think 23 guests (I gave them a low number in case we didn't end up with as many guests as I thought). This gives you a good idea of cost.. of course this will vary depending on when and where you are planning to get married and how many people you end up with