What does the word "margins" have to do with "доходы, прибыль"?

There is such a meaning:https://studyenglishwords.com/words/margin

Is it you again who put the thumb down?

Longman dictionary of Business English gives one of definitions of "margin" as " the difference between the cost or buying price and the selling price, i.e. gross profit"

Словарь Accounting Auditing Finance, изданный при содействии Ассоциации дипломированных бухгалтеров Великобритании (АССА), дает перевод narrow margin - небольшой размер прибыли