> There is the Law of Demand

What is this?

Demand functions (price as a function of quantity demanded) take all kinds of shapes. Veblen goods are the silly example of wrong-sloped demand [1]. The in-vogue example of sigmoid demand, however, is hot water–make hot water (or lighting, for that matter, as another comment today pointed out for LEDs) cheaper and there is a limit to the things we want hot water for. Halving the cost of hot water doesn't induce much new hot-water demand, it increases demand for other goods and services.

[1] https://en.wikipedia.org/wiki/Veblen_good