If a 60 watt bulb lasts 1000 hours at $0.10/kWh, that's $6 even if the bulb was free. So quadrupling the price has negligible effect on its total cost ($6.25 v

If a 60 watt bulb lasts 1000 hours at $0.10/kWh, that's $6 even if the bulb was free. So quadrupling the price has negligible effect on its total cost ($6.25 vs $7.00).