Do you mean 500Wh rather than 500kWh? 500 kWh would be around 10 EVs worth, and looks like it costs around 700k [0], but 500Wh seems to be a common size for portable power stations [1]

[0] https://www.backupbatterypower.com/products/516-kwh-industri...

[1] https://www.ankersolix.com/products/535?variant=497024349310...