One regular brick weights 2.3Kg, has 1000J/Kg/K specific heat capacity (0.278Wh/Kg/K) and costs $0.50 in bulk. Heated to 1500C one brick stores 0.278*2.3*1500=959Wh of heat. $0.5/0.959=$0.52/kWh (t) storage capacity cost. Compare this to $100/kWh (e) storage cost for batteries.
[pdf] Energy storing bricks are a novel form of concrete that aims to transform ordinary bricks into devices that can store electricity and power devices. It uses a chemical process to convert the red pigment in standard bricks into a conductive plastic that coats the pores inside the bricks.
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