Overhaul costs are part of the reason turbines are not too popular on GA aircraft.
To overhaul a 6 cylinder piston engine costs in the region of A$35,000. To overhaul a simple turbine starts at greater than A$100,000.
The other reason is fuel consumption. At low alttudes a turbine consumes a lot more fuel per horse power generated than a piston.
Maintenance licensing is also more difficult as all turbines have a type rating requiring specific courses where as a pistons up to a certain power (from memory 500 Kw) are under a group license and don't require specific courses.
Cheers
Trash Hauler