Disclaimer: I work in the carrier/service-provider facing side of the VoIP industry and have done a lot with inter-carrier reciprocal and access settlement in the US.

Be that as it may, passing the vicissitudes of such cost structures to the end-customer is a form of intentional obfuscation. It reflects a desire to bamboozle the customer, and also shift more risk onto them. For some reason, it works elsewhere in the world, but doesn't work in the US from a marketing perspective; your cell phone air time costs the same irrespectively of the jurisdiction you are calling, which can range from standard NECA tariff metro RBOCs to ultra-expensive rural ILECs wielding huge access charge forebearances (e.g. ye olde Iowa free conference calling scandal), and therefore, regardless of what the IXC hauler charges the mobile operator to get the call out of the Bell tandem and to the terminating LEC.

My point is, the variable cost structure of any non-trivial business has thousands of variables that can change on a monthly, daily, hourly or even per-minute basis. It is the job of any reasonable business to digest that through a risk management formula, statistical forecasts, etc. and arrive at a set of assumptions that can be presented into a standardised pricing structure accessible to the customer. The price can fluctuate based on market segmentation and salesmanship (airline tickets, enterprise software, etc.) but it cannot possibly involve a set of thousands of simultaneous equations that are up to the customer to (very improbably) mentally solve in an (improbably) adroit fashion. That is something only healthcare gets away with, as well as inter-business settlement regimes that have well-oiled processes for dealing with complex assessments.

Can you imagine if the bus fare changed hourly based on the precise availability of routes, drivers, who is out sick that day, how much overtime was owed last night (if applicable), etc?