Earlier quoted context omitted.
The reason for inequality is that people are not equal. The work they do produce is not equal in value. More people can do a janitor's job, and/or do without a janitor, so the value of a janitor's work is less. More supply, elastic demand, means lower price point. Through technology, some people are able to produce much more than others, so inequality is inevitable unless there is a balancing force (aka taxation).
Your first paragraph, on supply and demand, is fairly accurate, but to say that "some people are able to produce much more than others" is oversimplifying. Consider a fast food restaurant with one cleaner, two people at the tills, three people in the kitchen, and one manager. Remove any of them and the lines will become too long, the place will become unacceptably dirty, etc. However, none of the employees is "produc…
The people that developed email and whatnot produced more than the people who deliver mail, etc.