Google Site Search is priced to be affordable to a wide range of different organizations. With this edition, you get ads-free search results, access to Google for Work technical support, the ability to completely change the search results via XML feed, and the option to remove the Google logo from the search box and results page. These features allow you to fully integrate a Google-powered search feature into your site, and enhance the experience for your visitors to your site.
The free version of CSE includes advertisements, mandatory Google branding, and fewer customization options. In order to disable ads on your free CSE, you site must belong to an organization recognized as exempt from taxation under section 501(c)(3) of the U.S. Internal Revenue Code. Outside of the U.S., this is available to charitable organizations as defined under country-specific regulations or requirements, but would need to upgrade to Google site search for the other features of business edition.