Estimating Vacation Costs
Traveling to WDW will almost certainly result in a fantastic vacation, but it won't come cheap. It's best to compare the expected cost with your budget well in advance of the trip, so you don't have to worry about nickels and dimes during the vacation.
The three seasons that Disney uses to divide up its' year -- and which defines the general level of price for accommodations -- are value, regular, and peak seasons. Not surprisingly, prices are lower when demand drops. On the other extreme, prices go way up during the busier times of the year.
Rack rates for moderate on-site accommodations range from $160 (during value season) to $250 per night (during peak season) including state and county occupancy taxes. Cost can go up significantly if you decide to stay at a premium or home- away- from- home resort, but you can also reduce your cost by staying at one of the value resorts. Note that the best discounts (those given to Disney Club members and theme park annual pass holders) are available during value season and are almost non-existent during peak season. You can see rack rates for all of the Disney resorts by reading through the WDW Resorts From A to Z page. One last thing on accommodations prices -- don't forget to plan for the 11 to 12% county and 6% state room taxes!
The cost of staying at an offsite resort can vary even more wildly, so consider what you're willing to spend and do your shopping well in advance of your trip to ensure that you get your accommodations at a price you're willing to pay.
... and Board
As far as the food budget goes, you should plan on spending $30 per day per person for food (less for children and/or light eaters) as a rough, but conservative, number. This assumes that you'll be enjoying one nice sit-down meal each day (either a brunch, nice lunch, or dinner) and a couple of less expensive meals at one of the fast food eateries on site. You can stretch your food budget considerably by having some meals (a light breakfast, for example) in your room and by having fewer upscale meals spread throughout the trip.
You should also plan on spending an average of $40 per day per person for admission media. Of course, the longer you stay, per diem costs for admission media will drop (assuming that you purchase multi-day passes). You can save some money by taking advantage of the Disney Club discount. Also, annual pass holders get a discount when they renew their APs (versus the price of the original annual pass). You can see the prices, and a lot more information on admission media, by reading through the Admission Media From A to Z page.
Souvenirs and Sundry Stuff
I would also suggest that your budget include a certain amount of money for souvenirs for each member of your party. The Walt Disney Company is a marketing empire. You will wander through stores, pass by small shops, and around pushcarts strategically located throughout the Walt Disney World complex. For example, the exits of many of the premier attractions dump you right into a themed shop while you and your kids are in a happy mood and are most likely willing to part with more cash. The absolute worst offense of the Disney marketers, though, is that there's so much fun, high quality (and high priced) merchandise available. There's a lot of junk, too, but much of what's on the shelves is good stuff -- and that just makes it more difficult to walk past those displays without buying.
As a result of these tricks and traps, almost everyone in your group is likely to find something that they want to buy during the course of your trip. It's a lot easier on the pocketbook if you determine up front what you're willing to spend. A typical person can easily find at least $50-$100 worth of souvenirs -- or more -- that they would love to cart back home. Plan accordingly -- or take the necessary precautions (i.e. pre-trip education) to avoid problems when little Susie or Johnny find that $375 Disney University Leather Jacket that they "just have to have."
Let me make one last observation on this matter. There are three schools of thought on souvenir shopping at WDW. The first is that you should snap up anything you see and want because you probably won't see it again (because it's sold out or you simply can't remember where you found it). The second is that you should shop around and see if you see the same item for a better price elsewhere (often identical items at the Village Marketplace are priced lower than in the parks, for example). The third is that you should shop around and see if you will find a different item that you would rather have. You'll have to decide which of these works best for you.
The Final Budget
All of these numbers are conservative ones that are good for budget planning, but you should get hard numbers from your hotel and Disney (for admission media for the duration of your trip) as soon as you can. For one thing, it locks the prices when you make your reservations... for another, you'll know exactly what your costs will be.
Don't forget to include money in your budget for the trip to WDW and back home again. Airfare and/or gas and lodging costs can be estimated, or you can call a travel agent to get an idea of the costs for the time of year you are planning on going.
Before You Book Your Trip
Let me put in a plug here for a site that has already been extremely valuable to many trip planners. MouseSavers.com provides a TON of information on saving money for a Disney trip (and that includes all of the Disney resorts, not just Walt Disney World.) It's well worth spending some quality time going over the savings ideas and taking advantage (if at all possible) of the various discount codes that are provided.
After you're comfortable that you can afford the amount of money that you've budgeted for your trip, do your shopping and diligently work until you get prices that fit your budget. Then, after you're left home, stick with it! There's nothing worse than coming back from a great vacation to a pile of bills that you'll work for months to pay off. Instead, be disciplined and keep to that budget, and you can reward yourself with another vacation perhaps a bit sooner than you thought possible.