Costs and Expenses

They're the same. More or less. They exist on an income statement.

The dog collars cost you a dollar to make. That dollar showed up as an expense on your income statement. Sometimes costs are conceived as the total cash or financial commitment to making something, whereas an expense is the accounting attribution of those expenses...but in this phrasing, the whole thing is pretty unclear. Using the terms together in one phrase is kind of a repetitive, useless thing; kind of like saying that the lawn-mowing will be done in "two hours' time." Like...why do you need to add the word "time" in there? Is there a two hours that's not time, at least on Earth?

See: Income Statement for more on this odd phrase.