Others have pointed out the catch to subtracting the debt of the people with negative net worth from the wealth of people with moderate incomes. No need to repeat that.
Let me also add that such statistics depend greatly on how one calculates wealth, and the definition can make the results very misleading.
For example, you often read statistics like this page, https://www.givewell.org/international/technical/additional/Standard-of-Living, that says that economists calculate "the number of people living on under $1.25 a day at about 1.4 billion worldwide".
A little thought will show that that cannot possibly mean that their lifestyle is comparable to that of someone in America or Western Europe trying to live on $1.25 per day. I sincerely doubt that it would be possible to buy sufficient food to live for $1.25 a day, never mind other necessities of life.
Not to say that these people are not extremely poor. I certainly wouldn't want to switch places with them. But they're not THAT poor. They get these statistics by ignoring many forms of real wealth. Many of these people are subsistence farmers. They own land for farming, or live in a culture that pays little attention to the idea of legal title to land. What would be the market value of this land if it was in Los Angeles? By that standard some of these peasant farms would be quite wealthy. They may hunt animals for meat and use their skins for clothing. What is the market value of this? These things are not counted in these statistics. Etc.
On a less dramatic scale, you often see statistics contrasting the wealth of the richest Americans to the average Americans. According to this page, https://www.thebalance.com/american-net-worth-by-state-metropolitan-4135839, "The concentration of wealth in the U.S. continues to deepen as the top 1 percent of wealthiest U.S. households now holds 24 percent of liquid wealth. Non-affluent households, representing 70 percent of U.S. households, control less than 10 percent of the nation’s liquid wealth."
Of course rich people are richer than poor people -- duh -- but the situation is not as extreme as these numbers make it sound. The subtle key word in that statistic is "liquid". "Liquid wealth" is cash, stocks and bonds, and the like. It does not include houses, cars, appliances, furniture, and other such assets.
Suppose person A owns a house worth $200,000 with no mortgage, a brand new $30,000 car bought with cash, a $50,000 boat, and tens of thousands in other assets, but has only $5,000 in the bank, while person B lives in an apartment and doesn't own a house, doesn't own a car but rides the bus, and in general has few material possessions, but he has $50,000 in the bank. Would you say that B is 10 times as rich as A, because only the cash counts as "wealth"?
Realistically, most people spend a considerable percentage of their income on things that are quickly consumed: food, gas for the car, electricity, etc. After that they use their money to buy things that they want to use in their daily life: houses and cars and furniture and the like. It's only after they have these things that they put substantial money into savings and investments. (I'd say most Americans put too little money into savings, but that's another story.)
So suppose you have two people. A has earned $500,000 so far in his life. Of this he has spent $200,000 on things he's consumed, $250,000 on durable assets like a house and car, and he has saved $50,000. B has earned $750,000. Of this he has spent $250,000 on things he's consumed, $300,000 on durable assets, and he's saved $200,000. So B earned 50% more money than A, but his liquid assets are 400% of A's. (I just made up those numbers, I'm not claiming they represent any actual case histories, but I think they're not implausible. There are people out there in these general ballparks.) Yes, B is richer than A, but counting just liquid assets exaggerates the difference wildly.