CubeCart
From the official CubeCart website:
CubeCart is a powerful eCommerce script written with PHP & MySQL. With CubeCart you can setup a powerful online store as long as you have hosting supporting PHP and one MySQL database.
To learn more about this e-commerce solution and all the other e-commerce solutions that Wallanet offers go here: http://www.wallanet.com/open_source_packages/e_commerce
Price: $179.95