$ aside, you do need paying directors in any organization,
even charitable or non-profit. they are the ones who have the
leadership skills, vision, the contacts with the higher up,
organizational skills that keeps the organization going. the
structure will decide how many paying staff is needed, because you
need continuity in the organization. executive part-timer doesn't
work.
the question then is what is the fair amount.
I hope you don't mean that the work done by volunteer are
unimportant. I also hope that you don't mean that non-org skills
are trivial that they can be unpaid.
Leaders by themselves are inadequate, the followers who do the
actual work are also important, FYI.