Charging for cables, wall plates, etc. is what you're supposed to do.  Charging for anchors and small miscellaneous parts is excessive and probably not worth the time it takes to do the calculations.

On top of that, I think if you try to charge for each and every minor little detail, the billing takes considerably longer, and exceeds the actual money that you're making on the parts.  

My recommendation?  Keep it simple. Charge enough to cover those types of parts and be done with it.  People like simple.  

People don't like being charged for ever little "minor" piece that's needed.  

If this happened to me with a service contractor in my home, he'd never be back in my home.  

I suppose you could break this down into the Law of Diminishing Returns..How much more time is spent charging for every minor detail, rather than just building it into the price. How much time is spent on that every day, week, month, and how much of that time could be used to bring in bigger projects that would pay dividends over the small parts you're charging for.


There's an old saying in sales/finance.  

"Pigs get fed, hogs get slaughtered"