If you were venting your grow and venting heat out of the house and used electric heat during the winter then a 75w light could add 100 a month or more to your bill, all based on how much heat you were venting out of the house and needed to be recreated. Other than that, no, bullshit.
If you want to grow more without extra cost, call your electric company up and ask about different rate plans. Most have an option for a time of day plan where you can have very cheap electric in off peak hours and grow then. My off peak is 4-5cents a kwh and on peak is 3-4x that, but we just conserve electricity during peak hours and even growing with 2kw was cheaper after we changed plans than it was with no growing on the original plan. If much of your electric is heat and you stop growing even it still works out fine too, because peak is daytime and warmer, and most of the heat you need percentage wise is night time.
FYI with no growing at all our average electric bill cut in half or better on the peak plan. Winter months that were often easily over $200 a month became as low as $75 a month. With 2kw growing on the new plan it was still cheaper than no growing on the normal plan.
But before figuring all the above out, while venting 2kw of heat outside we were getting absolutely hammered, the bill was scary. Get a carbon filter so you don't vent the heat you create with your lights, you recycle it into the home and it offsets your other heat and works out about even. Most of the power you put into lights is wasted in the form of heat, our lights even HPS are actually very inneficient.
