If you are unfamiliar with Action Game Maker (AGMaker), it is an game framework being made in Godot by Gotcha Gotcha Games, the Japanese company behind the RPG Maker series engines.
This is a successor of Pixel Game Maker MV and is made by the developers of RPG Maker. So yes it will be paid similar to RPG In A Box, but it will come with a framework to start building games right away (useful for non programmers). They designed it in such a way to keep up with Godot updates as well, which is pretty interesting knowing how GGG usually design their products.