The first generation sodium ion are a bit cheaper than LFP but the volumes will not be worldchanging. However, the second generation sodium ion could reach $40 per kWh. Iron LFP batteries could get to $50/kWh with really high volume and efficiency at the cell level. The future low price of sodium ion would make for insanely cheap fixed storage products like the Tesla Megapack and Powerwalls. They also do not have practical material limits. There is no shortage of salt or soda ash. The United States has about 90% of the world's readily mined reserves of soda ash. Wyoming has 47 billion tons of mineable soda ash in the Green River basin. There would be hundreds of TWH of power storage from each billion tons of soda ash. Based on material costs of $4 per kWh there could be $8 to $10 per kWh sodium ion batteries in the future. This would be ten times cheaper than energy storage batteries today.