When using Google Adwords there is a cost based on a PPC (Pay-Per-Click) or based on the number of displays. Your cost will depend on the number of displays and on the number of visitors that click on your ad. This ads need to be properly configured, as they can become very expensive very quickly if they are displayed too often and to unnecessary users.
Using SEO services implies higher costs initially, but the return of investment will also be higher, because of the long lasting effect of such a campaign. Another benefit is that you can always adjust the keys you would like to have your website indexed against.
If you to see our SEO Services or you want to learn more about SEO visit our site http://www.seoplus.co.nz. In the resources section of our site you can find some SEO Tools and a SEO dictionary.