While that makes sense if the top-level universe follows our laws of physics, we can’t guarantee that the top-level actually has to follow the same rules as simulations. Perhaps energy and/or matter can be created from thin air, meaning that there are no issues of conservation of energy or matter. A universe like this has literally limitless energy, and so the amount of energy it uses to simulate universes, either separately or within other universes, becomes negligible or a moot point. Perhaps the simulators are more interested in what their simulations simulate rather than their own simulations; perhaps they’re trying to create new patterns of thought that they can’t imagine to create themselves. There are just a lot of questions with Simulation Theory.