Drupal has "multi-site" capabilities - meaning you can have one instance of drupal supporting many different domains. This can be done with a single admin backend and a shared database, or a unique database and admin backend for each domain. There is an obvious cost advantage, once the first site is built the additional sites can be setup for about 1/2 the cost (not including the content). And this supports the excellent SEO strategy of setting up "mini-sites" for marketing purpose with specific urls that will perform well in SEO & paid search - like the site you are looking at now.