As you have correctly summised I struggle to do 100hrs a year, this year about 75.
Generally the hourly cost for fuel is about $105. The annual maintenance cost is about $5,000 including annual / 100hrly and unplanned work. The insurance cost is about $5,000 per year. The props and engine are about 2,000 hrs TBO and a prop is abour $14K and an IO-320 about $40K therefore allow about $110K every 2,000hrs or about $55/hr for these items.
It is expensive but the twin comanche is a very honest four seater, in my case a family of five (three kids on the back seat is allowable as long as their combined weight is less than 155kg). We usually take alot of luggage and generally full tanks, 428ltrs. At a burn rate of 66 lph that equates to nearly 6.5 hours at a TAS of 162kts @ 7,000 ft.
BEW 1120kg
MTOW 1690kg
Hope that helps, how does this compare with say a Jabiru or CT?