An SEO campaign can take time to take effect because the search engines run on their own schedule. Sometimes they purposely lag in order to not be unduly influenced by short-term factors. So, be prepared to wait 6-9 months before you see the full results of an SEO campaign, and if it comes sooner, then you can be pleasantly surprised.
It's common for businesses to spend more on internet marketing than the website itself. A business that spends $20,000 realizing a new website can reasily spend $5,000 per month on Google Adwords. Consider that internet marketing almost entirely replaces traditional paper advertising for most businesses, and think about what you have spent on newspaper or Yellow Pages advertising in the past.
If you rely on your website to attract new prospects through search engines, then you'll probably need to make special efforts — such as SEO and PPC Ads — for search engine visibility. Just because you have a new website doesn't mean that customers will find it. In fact, many people make the mistake of thinking that a new website will automatically rank highly in the search engines, but this is not the case.