In short
Walt Disney World covers an area the size of San Francisco, with four parks. Universal has three, and SeaWorld two. None of them is in Orlando itself.
The Kennedy Space Center, an hour away on the coast, is the one site in the region that is not a theme park.
What it really costs
Park tickets are the dominant item and they are dynamically priced: the same day costs anything up to double depending on the date. Multi-day tickets bring the daily price down sharply.
Accommodation outside the resorts, in Kissimmee or on International Drive, costs a fraction of the park hotels, but requires a car.
What nobody tells you
A car is essential: the parks are spread over tens of kilometres and public transport does not link them. Parking is charged at each park, each day.
Queues are handled by paid booking systems, separate from the entry ticket and different at Disney and Universal. Not buying them means spending the day waiting.
June to September combines heat, humidity and daily late-afternoon storms that empty the parks for an hour. It is also hurricane season.