It’s not about what you charge to get the work; its about what you charge to come out with a profit you are happy with.
You must know what it will cost you to do the work and then profit. Add your wage to the cost of doing the work and if the customer wants a better price take it from profit only after you tried the give more at the same price.
I work in sales and its always better to give a bit more for the same price rather than taking money out of your pocket.