Rogers words are gospel!
You also may be giving your customers the thought that you 'charged to much' for the regular work, and they will beat you up more.
The resi guys that I know MAKE THERE MONEY on extras that the HO's want on new work. The builders are real tight, and resi is very competitive here. (I don't do resi, only comm)
Do I give my comm clients a 'break'? Occasionally a 'good will' jesture, but I have 4 guys to pay, insurance, etc. and I have to make a living also.