An important piece of how well-off you are, which measuring income isn’t really going to catch, is how much shock absorption your community has built in.
Some people don’t have an in-person community, of course, and so the shock-absorption available to them is just whatever is in their own savings account and how much credit they have access to and maybe the knowledge that in the worst case they could move across the country and sleep on a friends’ couch for a few weeks but not longer because the friends’ landlord is strict about subtenants.
On the opposite end of the spectrum, upper-class communities have tons of shock absorption - if your home burns down, you probably have a friend who has a vacation home or an in-laws suite or a guest room where you can stay, if you lose your job it was the kind of job for which you get unemployment and you know someone who can get you an interview for another one, if you have a medical crisis you have lots of friends who can bring food and help out, and they all work jobs that let them take off on short notice in the middle of the day.
I’ve been helping a friend recover from surgery this week, and I’ve been thinking about this a ton. I could work from home for three days to be with her; her girlfriend had a spare bed where she could sleep for two because she was supposed to be near the surgery center and her house was an hour away; her girlfriend’s boyfriend could come over to help when girlfriend had to go to work; when her doctor’s appointment was changed to a time when I couldn’t drive her, another friend could take three hours off to do it. That’s a community with shock absorption.
It’s a class thing, but it’s not just a class thing. Doing this sort of thing is one of the things religions do. When I describe what I value about my community, my religious friends tend to go “oh, so, like what my church does”. A poor community where a dozen people from church will bring meals and support after surgery or after a loss or during cancer treatment has vastly more shock absorption than a same-income community where people have no way to coordinate that (and I think the decline of religion has been particularly costly in poor communities for exactly this reason).
And lots of money can’t fully substitute for a community, because lots of disasters (like medical emergencies) are of the kind that make it hard to advocate for yourself and independently arrange all the things you’re going to need.
I don’t know how you increase shock absorption. Lowering the cost of housing does part of it; a spare bedroom is a particularly critical kind of shock absorption that protects lots of people from homelessness. More leisure time increases shock absorption, and cutting the expected work week has been at least partially successful some places. My impression is that Social Security dramatically increased shock absorption, by giving elderly people (who often end up needing community support to remain independent or survive) more financial resources; it’s much easier for poor families to take someone in if they will get regular money towards housing and expenses. UBI would do it too, of course.