Is it really cheap? I would strongly disagree with this statement. Firstly, if you want to increase your search results - you are going to need to do a lot of work. If you run a company that has a website on the Internet, you are going to need people working on your SEO, which means you will need to pay them for the work they do. As the very minimal requirement would be to have at least three people (that would probably even wouldn't be able to make a significant change) - one analyst (who would seek the latest SEO tendencies, would do keyword research and etc.), content writer (one person can write about 7-8 quality SEO posts per day, will it be enough for you?), your SEO manager that would actually distribute the work and would make the decisions on what is the priority of the company.
I will have to agree with Vincentas. SEO is not a cheap way on marketing a business. The process will get much of your time, effort and money for you to get your desired website rankings. Also, you need to pay the people who are doing the SEO process in your website. Therefore, the SEO process is not cheap.