Medical devices, wireless headsets, phones, drones, various pro-grade cameras and gear - there are many devices where expensive batteries would still be economical.

For some apllications, you need fixed amount of power, perhaps you could have 3 times less batties, at 3x the price. That frees up space and reduces weight.

Would somebody buy an IPhone with 1-week charge, if it was double the price? Probably.

Cost of manufacturing something like this can only go down and there are plenty of applications where mass or power output/battery life of a device is much more important than cost.

Depends on what proportion of the BOM the electrodes represent. If the electrodes are, say, 1% of the cost of making a battery, than a 1000% increase in the cost of the electrode only adds 9% to the cost of the battery.