It's funny but in the UK there seems to be a culture for not charging for ground work
...or for signing random visiting pilots' paperwork, or for keeping up student notes, or for maintaining aircraft tech logs...
The list goes on. I think it stems from old CAA 'advice' not to charge for signing log books. I never do, but I know of at least one club that has started charging.
In some cultures, such as gliding clubs in the UK, instructors are unpaid. I believe this is also the case in many powered flying clubs in France.
TOO