KVR Marketplace is described as 'shop created for plug-in, application and soundware developers to sell their products directly to the KVR Audio audience of passionate and informed music-makers'. There are three alternatives to KVR Marketplace, not only websites but also apps for . The best alternative is Producer Bundle, which is free. Other great sites and apps similar to KVR Marketplace are Pluginboutique (Freemium) and VSTBuzz (Paid).
VSTBuzz showcases and provides great deals on audio software and bundles. It's sort of like Humble Bundle but for music apps, with timed offers on hand-picked audio gear to help you find the best at unbeatable prices.