There are scaling problems. For example, try to compare Exxon with a smaller oil producer (XYZ corp). Exxon had net income of like $30 billion last year. Let's say XYZ had net income on $200 million.

Will you look at those numbers and say Exxon is making obscene profits and the XYZ is more reasonable? No, you really can't make any kind of judgments based just off of those numbers.

Profit margin says how much of their sales actually turn into profits (as opposed to covering costs). If Exxon and XYZ are identical except for the fact the Exxon has much more customers, Exxon will have much higher profits.

Last year, Exxon had a profit margin of about 7%. That is for every $1 of stuff they sold, they profited 7 cents. Is that obscene? How about compared to other industries?