300 watt 120v ge light bulb cost.?

You pay for energy by kwh of energy used, bulb is 300 watts that's 0.3 kw if it's on for 10 hours it's 3 kwh, you then need to know the cost your energy supplier charges per kwh, uk is 20 pence sterling and usa 12 cents 3× 12 =36 cents ( kwh × unit cost per kwh)

So this halogen bulb uses 36 cents for 10 hours use. Cheaper would have been a cfu lamp (compact fluorescent) which would have been probably 30 watts rated for the lumens you quote, or 15 watts led lamp ( light emitting diode) for the same light output.

The incandescent lamp life is 1000 hrs, cfu lamp lasts about 6 yrs and the led 15 years. Obviously the cost of a cfu lamp is probably 5 times the indescent, and led lamp 10 times incandescent.

If the 300 watt bulb is only on for a few hrs then it's short lamp life is ok, if the lamp is lit longer then it's more economic to use a cfu or even led. Incandescent lamps when lit are a yellow warm light, cfu mainly a white light, and led a very bright white light.