Looking at Eggplantwalking's profile would suggest that epw is the instructor, not the student.
Personally I would have to say that I think reasonableness has to come into it.
If the student is a abinto student and is normally resonsible for land away landing fees then surely the instructor owes them a duty of care, and should warn them if they are landing somewhere that will cost them £100's if they normally pay £10.
However if the student is a qualified PPL or CPL and is a "student" training to add another rating onto their ticket, then maybe they should know better about where they are likely to be charged enormous fees, and the instructor may not have such a duty of care.
dp