One of the best things about working with a strong CMS like Joomla! and Wordpress is that there has been so much effort placed on the development of extensions specifically suited for vertical markets. A vertical market is a term used for commonly competitive industries that solve the same or similar needs. Many times there are industry standards for layout and information display that helps to guide the development of components that are specifically suited for your market.
For example most won't argue that if you have a website that deals primarily with Real Estate your site visitors will probably expect a photo gallery, a description, a map, a list of amenities, the number of bedrooms and baths, a price, and a contact number. It would also be expected that each property viewed would have this information displayed in the same place on each listing. Although there is always the occasion where a custom layout with custom information is necessary, using existing tools that have already been developed for your market is a great way to keep down the cost of a large site.
Many times we meet enterprising entrepreneurs that have a specific need and have found that by taking a vertical market component and modifying its use we are able to create a comprehensive site for a brand-new market while keeping development costs relatively low.