Too complex to list ... but not too complex to charge?!

Imagine scanning 50 things at the self-checkout at the supermarket and the machine says, "sorry, it's too many to list; you are getting an abridged receipt".

I believe the argument is that the passthrough fees can vary by location in a way that makes it hard to produce a precise fee calculation on promotional material. As a random example, it's plausible that a local government could charge a fee for installing new hardware in historic buildings; failing to include that fee when advertising to residents would fall afoul of the previous rule.

Of course, the counterargument is that ISPs should just be eating charges like that rather than passing them on to consumers. If they don't want to have to advertise confusing, long fee schedules, they shouldn't try to charge them in the first place!