>When someone drives past me in a car that I know costs the equivalent of 30 years of my life...
Even as a comfortably paid software developer, someone with a billion dollars owns the equivalent of ten thousand years of my life.
Now inequality has increased much more significantly. And you can't tell.
You haven't found a measure of inequality, you have identified that you can't afford an expensive car. Insofar as they are problems, the solutions to inequality and material lack are different from each other.
EDIT And furthermore, if inequality is the major problem, you're arguing you'd rather be in Scenario Now (no car) rather than Scenario Hypothetical (very expensive car). I don't like telling people their opinion, but I'd be shocked if inequality is going to be a factor in your decision making with that one.
It demonstrates that someone can afford an expensive car and someone else can't. That's not a measure of the extent of the inequality (the car owner could be a millionaire or a billionaire), but it's certainly a signal that inequality exists. I know that the inequality is at least someone having enough to spend 30 times what I earn on a car, and could possibly be thousands of times larger than that. That is a measure of inequality insofar as it clearly shows inequality exists. It's just not a very specific one that tells us the extent.
However if you doubled your living standard you'd know all about it.
This assumes that halving the wealth of rich people would have no impact on the world other than changing this immeasurable inequality. That seems unlikely.
Destroying the wealth would be the fastest and easiest way to reduce wealth inequality that has built up in the last 20 years. It is a terrible idea. So the problem to solve is probably not wealth inequality.
To try and put it simply, halving the wealth of rich people is bound to have an effect - but that effect might be great or horrific for everyone else.
Now, private jets and yachts...different story.
If your argument is that the person with a Lamborghini isn't materially better off in a real sense and that wealth inequality is therefore a social construction then I am profoundly confused if you are also aligned with the article's thesis that pitchforks are going to be involved due to wealth inequality.
The logical conclusion of that line of thought is to destroy the Lamborghini to promote wealth equality, which is stupid.
When someone drives past me in a car that I know costs the equivalent of 30 years of my salary I do have some idea of how unequal we are. It's a pretty big clue.