You can build apps for enterprises in two ways:
In App Stores: You can build an app at design.appmachine.com and publish these apps in the public app stores. You can put a part of the content behind a Lock-block. Apple requires you to make a large part of the content publicly available to make the app interesting for a large group of people.
You pay the normal reseller price for an app.
Enterprise license: If your enterprise customer has an Enterprise license from Apple, you are allowed to build apps and distribute them among your employees. You can build your app using design.appmachine.com. You enter the credentials of your Enterprise license and buy the app. AppMachine will build the app and make it available for you as a download from a URL.
You pay the normal reseller price for an app.