Online navigation mode is and always will be for free. Please, keep in mind that it requires constant internet access while driving for navigation to be able to download the map data and calculate the route.
The offline version is available in a paid subscription. After you subscribe to Premium, you will be able to download selected maps to your device and use it without an internet connection. However, Premium Professional includes online toll costs, and you'll need to have internet access to see the prices, but the data consumption would be low or almost none.