This is a lazy dismissal of any process or efficiency improvements.
If buyers care to pay for efficiency improvements, products with them will be more attractive to them. If they don't, they won't.
If your theory were true, we wouldn't have things like rechargeable batteries, low-energy appliances, or light bulbs that would last more than two months.
There's always some performance point when most people largely stop differentiating products based on efficiency or longevity improvements, and I'm not sure if consumer Li-I batteries are at that point yet.