It can be expensive, but it doesn't have to be.
That 2k for 6 days that someone mentioned is ridiculously expensive. But that includes staying at one of the most expensive resorts there is, in one of the most expensive units they have, during the most expensive time of year. And it includes paying for the all-inclusive meal package that includes full table service meals for breakfast, lunch, and dinner every day.
Yes, it's $70 for one day in a park. But you can also get a 10 day ticket for $240, making it $24 / day. Or you can add the water parks/disney quest/pleasure island option for $50. So for $290, you could get a ticket that would allow you to visit the theme parks on 10 different days, plus give you admission to the comedy and dance clubs at pleasure island, plus let you go to the 2 water parks several times. So for $290, you could easily keep yourself entertained for 2 weeks.
Some of the hotels are very expensive. The deluxes start around $240/night and go up from there. But they also have the moderate resorts (Port Orleans, Carribbean Beach, Coronado Springs) that are very nice and run between $130-$200/night, or lower if you get a AAA discount or a discount code. Then they have the value resorts, which are very basic, but a lot of fun for the kids and still get you on disney property and give you the perks that come with that for a price of around $70-$100/night.
You definitely pay a premium for food, but it's really no worse than the prices you'd find at any other location that has a captive audience and no competition. Our problem is that we always like to eat at the nice expensive sit-down restaurants. But if you want to eat quick service meals, it's not that bad. A fast food type burger and fries meal will cost you around 8 or 9 dollars instead of the 5 or 6 dollars it would cost you at McDonalds.
As far as Universal, yes the tickets are cheaper, but they also have a lot less to offer. Two parks instead of Disney's 4 theme parks and 2 theme parks. And as someone else mentioned, Universal charges $30-$50 per day EXTRA to get their Express passes, while Disney provides Fastpass for free. So that really makes the Universal tickets cost more.
No, you don't have to buy the Express passes, but if you don't, you'll be waiting in long long lines. And yes, you get free express passes if you stay in a Universal resort, but their resorts start around $250/night and they don't have any less expensive resort options.