Rick Durden wrote:

Operating costs for a Cherokee 180 based on about 100 hours flown per
year run $50 to $60 per hour before fuel. If it's flown less than
that the costs go up. Figure an absolute bare minimum of $35 per hour
for maintenance, more if you want to keep the airplane in nice
condition rather than just barely airworthy, $9 per hour as a set
aside for engine overhaul, $2 set aside for prop overhaul, $10-20 for
tiedown/hangar and another $10 for the incidentals that keep showing
up and you have a start at the calculation.

FWIW when we were letting someone else use our plane, we did not
charge him for a share of fixed costs such as hangar and insurance.

Our way of looking at it was we were going to keep paying these
costs whether the plane flew, or not.

If we wanted to share fixed costs we would have formed a partnership
and given the person a "say" about where we were based, who was doing
maintenance and etc.

Of course what's fair and reasonable depends upon the way the owner
looks at it.

Cheers,
Sydney