I doubt that could happen. The price is so low that it doesn't make a difference unless your sodium costs negative dollars.

I would say the bulk price of lithium ion batteries is the most you could possibly remove via materials changes. When smaller batteries are more expensive, that's based on factors that would also affect other chemistries. And the bulk price for laptop capacity, 50-99 watt hours, is $5-10 and dropping.

On the other hand the bill of materials of many gadgets is really low while having tight margins. If there are two $100 tablets on the market and the other can advertise a 30% longer runtime weighing 15% more at the same cost, it could be a differentiator.