Yes, purchasing more than 1 seat will give a discount on each additional seat purchased. This is based on the type of license purchased. Personal and Commercial Pro license holders can add additional seats by logging into their ShaderMap account.
Once you complete your purchase of a Pro license, all you need to do is log in to your ShaderMap account to download the license key file. Once downloaded, simply double click the license file or drag it onto the ShaderMap shortcut.