Popular content management system WordPress now has its own unofficial plugin store that caters not only for free plugins but also for premium (paid-for) ones.
The solution, called WP App Store, can be accessed from the WordPress dashboard itself and the whole purchasing process can be done from within the WP installation.
WP App Store is the has been released by a freelance WP developer from Canada called Brad Touesnard who devised a simpler way of getting browsing and acquiring apps without having to go through the convoluted process of purchasing product from individual vendor, downloading product files to your desktop, uploading the product files to your server/WP installation via FTP and activating the new product on the WP install.
It is likely though that WordPress will allow paid for theme and plugin developers to sell their services through the existing directory in the short term especially it turns out to be a decent revenue generator. Check the video below for a quick introduction to the WP App Store.