Search Engine Marketing or SEM is not the same as SEO because businesses pay for the listing or ad that shows on the page. The great feature of SEM is that your business can be featured nearly instantly on the First Page of Google. The down side is that if your keyword or phrase that you are bidding on is highly competitive, you could be paying as much as $10 per click to begin with.
Dentists and Lawyers can often pay $10 per click at the beginning of an AdWords campaign but after the ads run for several months and we have optimized the campaign, the price per click begins to drastically drop and my clients rate of return on investment increases!
By the time the investment or cost of ads declines, if you have also begun an SEO campaign, your keywords will start to trigger results on the first page of Google for no cost. This creates a perfect scenario. You could potentially stay on the first page of Google for your primary keywords and reap the benefits of more leads calling you and when you need an extra push around holidays, you then activate your AdWords account to help capture interest in new products or seaasonal products that do not have optimized content on your site yet. Over time, all the content will be optimized and you may not have to pay for ads. 🙂