I agree with Sparky. It depends on the customer and how well I bought the item. I'm going to mark anything up at least 10%, but if I got a good deal on a circuit breaker (say $10 for a normal retail $35) I would charge 20% over normal retail making my actual mark up 420%. I am always willing to load up on any item I know I will use eventually if the price is right. I just bought 100 GE 20 amp breakers because I could get them for $.70 ea.