Except on occasions where the core charge is used simply for profiteering. Example: Let’s say a vendor is offering a performance package (gas engine) that includes modified (ported) stock heads of a newer version of the same head (hemi), cam and headers. But the cost of the kit is inflated to an exorbitant amount which leads you to believe you are actually getting new castings of the newer version of head with performance modifications (ported) done to them. Where in actuality, they are taking the “cores” modifying them, and placing a fat wad of cash in their pockets for the effort.
What the consumer is left with is a performance package which costs more than the actual modifications to your original heads if sought locally and the loss of your OEM numbers matching heads.
This would be a basis for not going forward with a vendor’s core charge process. in this case it’s called a rip-off!