IMO, there's close to no bad usecase for batteries. In almost all their applications, they end up spreading out power consumption favoring cheap energy for expensive energy.

If a datacenter installs a solar array + a giant battery pack for their power, that's much better than them heavily relying on a natural gas plant to generate power when the lights are out.

The commercial options would fall further in price probably than consumer prices. If you buy in bulk, you do research to find the most cost effective options. That's a common pattern with many things. I don't see why batteries would be any different. If anything, I'd expect consumer batteries to have higher margins. Tesla batteries are a good example probably. At those prices, a Tesla car would be unobtanium. Obviously they charge a lot less for batteries that go in a car.

The reality is that many battery factories might be operating at 40-50% capacity only. Exact figures are hard to come by but there are lots of warnings about over production, surpluses, etc.. That spells a lot of trouble for some of the newer battery producers promising more efficient batteries. Because unless they price match, they price themselves out of the market almost immediately.

Why does it have to be zero-sum?

Why not commercial demand creates the economies of scale that bring the residential stuff down in price with them?