I'm guessing you read
THIS question about the tax rate at WDW (which is 6.5% across WDW, except at the All Stars resort, which is in a separate county, where the rate is 7%).
Regarding the prices listed by WDW for counter service and snack carts, the prices EXCLUDE sales tax. So, be sure to add 6.5% to figure out the complete price.
Bonus tip: Are you aware that WDW just added a new "Quick Service Dining Plan"? The new plan begins January 11, 2009, and will include, per person, per night, 2 counter service meals, and two snacks. You will also get one refillable resort mug per guest that can be used at your resort throughout your stay. The cost will be approximately $29.99 (plus tax) per night per adult, and $8.99 (plus tax) per child (ages 3-9).