where you have established a 'working relationship' with someone, i dont think its wise to start to nitpick a guy on what he charges for a paraticular job. as you said, he worked on another job for 100$ for the whole day.
and 150 isnt exactly a gross overcharge. if it were me, i'd want 75 bucks to drive over to someones house to change a light bulb. two hours at 75/hr isnt exactly out of line these days. auto mechanics charge in that range and they dont even come to your house.
now if he told you it was 500....
randy