That’s not really what it’s saying.
It’s saying if they sell less power then the cost per unit of power goes up. This is how all businesses work due to economies of scale. If you sell a lot of stuff then you can sell the stuff for less money and still make more money.
If you personally use less power then that won’t increase your price per unit enough to offset the savings you made by using less power.
Visio is similar in that the lowest plan doesn’t let you use many of the built in shapes.
You can add them yourself as images but loads of useful shapes for a network diagram, for example, are missing making it very inconvenient to use (I’m now using draw.io).
I can understand limiting certain functionality (like only having a web UI) but not making basic tasks unnecessarily difficult.