They can opt for different price plans for different extent of work. Some couple require postprocessing only for the images they select for their album. And all my packages are simply service with or without album. From there, they can choose a package that fits their budget, no trading of items and all.
You don't have to break down the detailed pricing like a hospital bill for the client, because end of the day, you just have to deliver the package stipulated in the contract. Like a set dinner menu, you need not break down how much each item cost because it gets very confusing after a while.