1) I've learned this one by now, but I know sometimes people forget....the hotel TAX. You're thinking the room rate is X dollars but forget the TAX is over $10 a night.
2) Food , food , food. Either you fight it by bringing in enough snacks, water, drinks and eating off site or you budget accordingly. I don't get upset over the prices anymore, can't worry about something we can't control.
Here's what we do for food, for what it's worth (I've posted this before so bear with me.)
First, we get a very nice two bedroom suite off-site. There are several nice suite hotels all priced about the same as an All Star. Since it has a kitchen, we can have breakfast there or the hotel offers a free breakfast.
So after a big breakfast, we pack a few frozen water bottles, some fruit, granola bars, etc. to snack on at the parks. We really don't have a "lunch." We'll also buy a snack here and there like the turkey legs, popcorn... Then we'll have dinner outside the park.
What I've noticed is after you do this a few years it becomes habit. And it's funny...as the kids get older and they appreciate money I heard my 12 yr old say "$7.50 for a bad cheesburger??" So I know my kids aren't "missing" anything. We spend the money on the good treats, not the overpriced average or bad meals at WDW.