OK I guess I phrased it badly. At a list size of 10 million, email will probably cost around $10K per month to service. With SEM you'll be lucky if it costs les

OK I guess I phrased it badly. At a list size of 10 million, email will probably cost around $10K per month to service. With SEM you'll be lucky if it costs less than $250K per month. So for every SEM placement, you can send 25 newsletters. So you need SEM to convert 25x better than email to get value from it. That might be possible, depending on the quality of your list, but my experience is that all companies eventually use email marketing because it's so much cheaper with big lists. I would question how you even got a list size of 10 million, or what you're hoping to get from direct marketing, if $10K per month is prohibitive.