We cant go with what IF's. When you provide the best service that the customer sees the value they will not call someone else. If I give them a reason to call someone else then it is my fault.If the next guy they have come over charges ~$169 less to do what seems to be very similar tasks - you look too expensive.
What if the next guy charges double then I look like a bargain.
I am changing four switches. Period. When we go to restaurant they charge us per plate regardless if we eat there or take it home. They will not give you a discount if you order more than 2 plates or more than two beers. Why should we as service providers do any different. We as service providers have trained the customer to treat us this way.Are you changing four switches in four locations or are you changing one switch in a four gang box and they decide to change the others while you are already in there?
As was mentioned I would have charged a minimum labor charge as this probably took less then an hour, I could still see in some instances mileage, dispatching fees, etc. but those are one time fees regardless of what you did (I prefer to not itemize such things and instead cover such overhead costs in the labor fees) - plus (the marked up price) of each switch used.. But with the internet then know how much the local hardware store charges for the switch and less your price charged to the customer, that is when they start with their questions. Do you go to a retail store and ask what their purchase price was on items you bought? Any that runs a business understands you mark things up that you turn around and sell, especially if your primary business is retail sales, if you don't you must add fees elsewhere to the total bill or you don't profit.You don't let them know what your markup cost was, it isn't any of their business anyway
I changed my way of thinking and I look at things differently.