Thank you! :D What we can tell you right now is that you'll only need to pay for the *main game once: If you pay for NDM on Steam, all future updates will be automatic, and if you pay on Itch, you'll be notified about new patches/downloads as they become available. That said! Given the game won't be finished for a while, we want to make sure the price reflects the amount of content available, ergo the overall price will be lower the earlier you choose to buy the game.
*We will be releasing optional side stories/DLCs between main game updates, which will need to be bought separately. These side stories will not be necessary for understanding the broader game though, and simply act as extra content.