There's a saying in the paid search world that says something to the effect of, "PPC done right is free." The point being that your paid search efforts, when done effectively, will generate more revenue than they cost.Though it's not as exactly cut and dry for other areas of digital marketing (such as hard-to-track performance metrics surrounding brand equity), the fact remains that ROI should always be a marketer's first priority. Nothing proves the viability of digital or inbound marketing more than return on investment.