careful its additive.
main cost is the time in the brooder as you will need to set up a area that's warm but where the chicks can move out of the heat. Heating a incubator is cheap but trying to heat a area is way more expensive.
under 10c a day in electricity
if you want the real cost then you will need to know the kwh charge plus the line charge divided by the hours in a month from the electrical bill,
you will also need to know how long the heater is on/off during the hour and what the max rated watts of the...