I assume this is the article (I read it today too): https://www.yahoo.com/finance/news/heres-much-earn-considered-middle-174020565.html
The ranges do vary depending on the number of people in the household. I would assume the wide range is to try to account for the vast regional and local differences in cost of living.
Where you live certainly makes a HUGE difference. However, according to the U.S. Census the median price of a BRAND NEW home in 2016 ranged from $291,000 to $323,000, so $400,000 probably is still an upper income home for most U.S. residents. https://www.census.gov/construction/nrs/pdf/uspricemon.pdfThe majority of people on this board who go to Disney on a regular basis are more than likely making more than the average for their area.
Middle class income #'s also depend on where you live. We live in what is consistently the wealthiest county in the US and the median household income is $125,000 as of 2016. But, then, you can't find a single family home under $400,000 in most of the county unless it's old and small. So, everything is relative. DH and I are in our 50's so our income is quite a bit higher than the median since age makes a difference too.
Families making less than 50k don't spend all their time planning Disney trips.
I read that article earlier and really disagree with the low ends of their ranges. A two-person household making $34,000 isn't what I would consider "middle class", unless you live somewhere with a VERY low COL.
I can't imagine surviving on $34k a year for a single person, let along a family.
The median household income in my town is $85,000.