Update: Paprika 3 for iOS is universal. You no longer need to purchase the iPad and iPhone versions separately.
Yes, the Mac, iPhone, iPad, Android, Kindle Fire, and Windows versions of Paprika are all developed and sold separately. You will need to purchase the app individually for each device you want to use it on. Licenses purchased for one version are not transferable to another version.
However, for each device type, you can install the app on multiple devices of the same type. For example, if you purchase the Mac version of Paprika, you can install it on up to 5 Mac computers, as long as they have all been authorized with your iTunes account. (Details vary depending on which App Store you are purchasing from, and are set according to their policies. For the Windows version in particular, see here.)
Once you have purchased Paprika for your desired devices, you can use Paprika Cloud Sync to keep your data automatically synced between all of your devices. Paprika Cloud Sync is a free service that we provide.
Some people have asked us why we price our apps this way. Each version of Paprika takes us considerable time and effort to develop. Paprika Cloud Sync requires ongoing resources to maintain. Our current pricing model allows us to provide you with a free cloud sync service and also funds the continued development of each app.