With Android, there are no barriers at all to setting up the SDK, creating an application, and installing the application on your own phone via USB. You can even go so far as to build and distribute the .apk packages to let anyone in the world install your application on their own Android phone. In fact, if you don't care about the Market at all, you can simply release, distribute, or even sell your application on your own to customers, and they have the ability to get your app onto their phone as easily as downloading it through their Android Browser.
The only barrier comes when you want to start putting your apps on the Android Market, at which point you must become a registered Android Developer, for the cost of a whopping $25, which then allows you the ability to publish apps to the Market.