If you're getting a theme from the official directory, then this part doesn't concern you.
However, when getting a theme from a professional theme store, you usually have two or more options regarding the license. As I mentioned earlier, the price range is usually between $20 to $100. Now, there are many licensing models, but the following two examples are the most popular web-wide:
- Standard, one-site license: This allows you to launch a site using the theme. It's the recommended choice if you're just searching for a theme for yourself and are not going to use it on other people's sites as well. This is the cheapest kind of license.
- Developer license: This is targeted toward developers and people who want to launch more than one site with a theme. Additionally, the package usually includes PSD project files and other mid-development files (note that some one-site licenses include those as well). Developer licenses can be as much as twice as expensive as standard, one-site licenses.