Presentation
Google is a fully automated search engine which uses robots known as "spiders" to search the web on a monthly basis and find new sites for inclusion in the Google index.
Pricing
Google does not accept any payment for inclusion of sites in their index, nor for improving the rank of sites. Google only offers advertising opportunities which are known as "sponsored links".
Submission Tips

Since Google automatically crawls the web and includes sites in their index, submission to Google becomes a totally unnecessary process which does not even guarantee the inclusion. "Over-submitting" is not penalized, nor does it improve the likelihood of your site being added to the Google index. Still, if you choose to submit your site to Google, note that only the top-level domain is necessary.

The best way to ensure Google quickly finds your site is to have your page linked to from as many sites as possible. Every site that links to your page is interpreted by Google as a vote for that page.