You have to distinguish between manufacturing costs and market price. The costs are going to be down as the volume is going to be raised massively, if a significant part of the car production is going to be electric. Which also implies that the free market prices are going to go up short term for all car manufacturers, who have not secured their own battery supply.
But for those who have, or even have their own battery production (Tesla), costs are pretty much guaranteed to go down, as measured by scale, industrial production is just about to start.
It is also not as clear as you put it, that you have to get a new battery pack after "10 years". With batteries having 50 kWh and more, longer lifetimes are to be expected. And unlike car engines, batteries don't fail randomly, they have a clear observable capacity loss. You can either decide to just keep driving your car, if you can live with just 70% of its original range, or update your battery, but then the old battery has a resale value proportional to its remaining capacity.
But for those who have, or even have their own battery production (Tesla), costs are pretty much guaranteed to go down, as measured by scale, industrial production is just about to start.
It is also not as clear as you put it, that you have to get a new battery pack after "10 years". With batteries having 50 kWh and more, longer lifetimes are to be expected. And unlike car engines, batteries don't fail randomly, they have a clear observable capacity loss. You can either decide to just keep driving your car, if you can live with just 70% of its original range, or update your battery, but then the old battery has a resale value proportional to its remaining capacity.