Assisted-Service SEO
While assisted-service SEO doesn't lift the hands-on work and responsibility of the SEO effort off your shoulders, it does support your ventures with the professional guidance of a consultant. In most situations though, settling for advice and assistance only allows you to bring down the costs of optimization significantly.
Hiring an SEO for consultancy purposes gives you the freedom of echeloned, progressive payment, and you only take money out of your pocket for services that you actually need. Once you have acquired all the information you consider necessary, you're done. When you think you need more, simply go back and ask for guidance in those areas you want to approach at that time.
Self-Service SEO
As the name suggests, with this approach you are completely on your own. You are the one who decides both the direction of the SEO campaign and the main course of action, and to make things happen, you will have to look for relevant information at conferences, specialized workshops, forums and blogs, etc. In essence, self-service SEO allows you to save money, but choosing this route can at times be confusing, not to mention it will swallow a lot of your own time.
There is nothing wrong with the DIY approach, it's just that you need to be sure you know what you're plunging into. Most business owners see it as a temporary measure, and only resort to it when they are sure that their efforts will pay off later down the road.
SEO and the Question of Affordability
SEO doesn't have to be expensive, and the costs of specialized services are relative to the results promised. Before hiring a particular SEO service, always do a brief costs-benefit analysis and only close the deal if you consider the investment worth it.
Ultimately, the secret to keeping your SEO costs down is the efficiency factor. Achieving the most efficient balance between resources like time, money and other aspects with an impact on the success of your efforts is imperative for keeping your SEO campaign affordable.