Cost-wise, a standard household bulb (such as a 60A19IF) retails for around 85 cents, a standard reflector bulb (such as a 50R20) costs around $5.50 and an MR16 (such as the GE Precise brand) will run around $8. Replacement-wise, if you left the lights on 8 hours a day for 7 days a week, the household bulb would need to be replaced every 13 days, the standard reflector bulb would need to be replaced every 35 days and the MR16 would need to be replaced every 107 days. Of course, if I left the lights on in our house 8 hours a day every day of the week, I would be shot.