The American median income is around $45-50k so pretty much by definition any 5 digit expense is a big deal for the middle class. More importantly, however, you have to look at the amount of money people have leftover for unexpected expenses – a ton of people are living close to paycheck to paycheck even if they have median or better household income. They’re middle class by any common definition but fragile.
That sounds more like "petite bourgeoisie" than actual middle class. I know there was a lot of effort to redefine the term, but imo median income has little to do with it. If you live paycheck to paycheck you aren't even petite bourgeoisie.
No idea why you think median income has any relevance here. You could of course define "middle class" like that, but that is not the actual meaning of the term. I think in Western societies your middle class is at best 10% of people nowadays.
And just to add: I think this widespread redefinition of what middle class is not an accident. It seems quite effective, if you think 50k USD is middle class in the US. It wouldn't even be middle class in most of poorer Europe. The idea of term is completely unrelated to relative income, but rather a different social status; that isn't the case if you live paycheck to paycheck. And this redefinition is happening to obscure the fact that a large part of our population in the West had a loss in living standards over the last decades.
