Yes both energy density and specific energy will increase by 50-100%, which is where most of the cost savings come from. Also SSBs can be stacked into multi-cell modules (so multiple 'slices' into a 'brick') which further decreases the number of cells and reduces cost.Will the energy density be much improved? Will solid state batteries likely come in pouch format since there's no liquid electrolyte to contain?
The price to pay is a much lower C-rate (~1C) which reduces power output and charging speed. However with 50-100% increase in range charging speed will not be as big a concern as today. To make up for the lost power they need something like a hybrid battery or supercapacitor for high performance vehicles.
TM3 became so cheap because of Tesla's early switch to NCM811 which uses half the amount of cobalt (the most costly material in the cell) as NCM622 most competitors are using. They will transition to the even more aggressive NCM9.5.5 chemistry to cut down Co usage by another half and push specific energy to >300Wh/kg. Tesla knows the inherent safety risk of NCM811 but they have by far the best thermal management system.