Is the sentence, “Wilt Chamberlain, the pro basketball player, was tall” a meaningful statement? If so, is it true?
Saying that anyone over 7 feet in height is “tall” is not false or meaningless simply because “7” is an apparently arbitrary number. It does not mean we need a supposedly “objective” measurement such as “has to duck to enter Building X” for the term “tall” to have meaning.
We could say that anyone over 6 feet in height is tall. This, too, has meaning. Is it true? Well, it’s less true than the statement about “7 feet in height” and more true than “anyone over 5 feet in height is tall”. Of course, this assumes we’re talking about human beings, and not redwood trees - or bonsai trees.
The point I’m trying to make is that “rich” is not a binary value. It is an inherently relative term, just like “tall”. Sometimes a term fits in such a wide variety of contexts that it makes sense to treat it provisionally as a binary value; it is a useful fiction. Hence, “Bill Gates is rich” is true unless we’re talking about a very strange grouping, possibly including cartoon ducks. Therefore, I have no problem with saying “Bill Gates is rich”, even though it might be more technically correct to use the word “richer” and give a comparison group.
On the flip side, I wouldn’t normally say that someone making $25,000 a year in modern America is rich. However, if someone were to say, “Compared to a large number of people in [some thirdworld country], someone making $25,000 in modern America is rich” I wouldn’t disagree.
Since “rich” and “tall” are inherently relative terms, context is vital. In order for, say, the top 3% of people with the highest incomes in one of richest countries in the history of the world to be considered to not be rich, you have to contort the context to a great degree. For example, you can compare them to the the top two percent, or maybe the top 0.001 percent.