[a4isms]

It's ambiguous, and not that clear-cut.

Expressions like "A 20% increase in sales" are almost never used to describe an 20% increase in the sales department's headcount or budget. Most people would interpret that as a 20% increase in revenue from sales.

"Cost of Sales (COS)" in finance refers to the cost of making a sale, including all the costs required to produce the good or service sold, not just the compensation and other expenses associated with a sales department.

"Sales" as a noun does often refer to teh sales department, but there are times when it absolutely unambiguously means that, times when it almost never is interpreted as that, and times when it could go either way and a word like "revenue" would be clearer, but that doesn't make using the word" sales" to refer to revenue wrong.