Unlike bidding in engine systems, search engine optimization is very different to show your product and service info to public, it's free! When showing your message in Google and other search engines, your page's message would persist some time until the ranking down. Also, if your message came into top 1 pages in search engine and position well, it's more reliable and valuable to public than ad bidding.
Although no pay for bidding, search engine optimization will consume a lot of your time and energy, you or your vendor have to spent much on how to optimize your website. And you have to face to a risk, because you can hardly promise your website ranking in top 10.
You may had heard a lot suggestion from some SEO service company, but search engine optimization in China is total different then other countries. First of all, you have to treat Baidu as the major search engine which take more than 60% market share in China. Second, Chinese is an ancient language which developed 5,000 years, only native speaker would know it enough, that's why Google was challenged by Baidu in topic that who know Chinese best. Third, since SEO work was hard to improve in a short term, some agencies could not follow basic principles.
The search engine optimization campaign can not calculate the work hours accurately, so how to measure the performance and what further plan for website when optimization time out? Another important problem is that, when optimization work meet the stimy from some technical problems or even manager's acceptance, it will take more time to discuss and concession.
When looking for a SEO service in China, you can give us a call for suggestion if available. For more information about how we work on search engine optimization, please refer the optimize topics.