When you plan for your site promotion, there are few things to keep in mind before working out a cost or make a budget.
I will make that as few questions to ask yourself or your marketing team.
How important SEO is to your website?
Do you want to make your website as a primary business gateway?
Do you know SEO is a continuous activity as your conventional marketing methods?
Do you know your competitor online?
Have you determined your keywords and targeted visitors?
If you say Yes, you probably know the importance of SEO and now you want to know how the process is going to be priced, and what factors determine your budget.
1. Your present site and its status.
If yours is a simple brand new site or a site which is not visible to any search engine – Your site will need Search engine readiness review and preparation. Commonly called as SEO setup. Your SEO consultant will start from this, and will make your site ready for Search Engine spiders, while they visit the site.
2. Your Industry/Market:
There is a difference between promoting a site which is selling houses and selling antique rocks. You know which segment would be more competitive and costs more to do SEO.
3. Link building efforts:
This is somewhat related to the previous factor, and based on the keyword and its competition determines the volume of link building efforts to be made. Link building will be a continuous activity, and mostly done on fixed monthly costs.
Finally, you should know SEO is not a onetime task, and can not be done for a one time fixed cost as your answer was Yes to the questions asked above.