I always balk at the idea of "middle income" vs "high income" etc. As an indicator of where people are in their overall financial state Accumulated Wealth or Net Worth is a much better indicator of one's financial health. Ask the average person what does being wealthy mean and the response you get 80% + of the time is, well if you make $xxx,xxx.00 a year then you are whatever. As they say, it's not about what you make, it's about what you keep. I read a recent article that suggested that to be in the top 1% of net wealth on the planet all you needed was $422,000 in net worth. Think about that of the 7+ billion people on the planet to be in the top 70 million in terms of net worth all you need is $422k. Seems like a lot but in the US if you take the equity in your house, your 401k or other retirement funds, and any retirement plan you may have and then look at the present value of your Social Security benifits then a ton of the 325 million people in America are in the top 1% globally. This gives me a totally different view of middle class and the cost of a Disney vacation.
That said, yes Disney World is an expensive vacation but it really caters to repeat business and multiple trips which for large families becomes expensive. Wife and I are 60, we go three times a year so we have AP's which cuts ticket cost, there are only two of us and she is retired and I get 6 weeks of vacation a year. We can go off peak, with AP's and have points to fly on SW airlines because of our SW Visa. We are going in February for a week using points for flights, and our AP for no ticket costs. We will stay at Pop Century and got AP room rates so our out of pocket cost for a week excluding food and extra purchases will be $1,000. Sure we had to pay for the AP's but that's a sunk cost so the incremental cost is a lot less. Hence Disney caters to the repeat business. One offs or once in a lifetime trips tend to get very pricey.
But when compared to many other vacations WDW is not completely out of line. If you fly, stay in hotels and rent cars for other trips the total out of pocket is comparable to WDW in many instances.
There are many ways to make it to WDW without breaking the budget.