Hi, Tony,

The two biggest increases will be in maintenance and insurance. I don't
have much Comanche experience but on our Arrow the extra cost for
maintenance of the gear and constant speed prop probably averages around
$600/year (much of which is for prop overhaul). But that cost is more than
offset by the lower fuel bills provided by the RG, compared to similar
performance FG airplanes. (175 hrs/yr X 3 gph savings X $3/gal = $1775/yr)

Insurance will be a problem until you have some number of hours in retracts.
Even after that, you will probably pay several hundred dollars/year more
for a Comanche compared to a 172.

I do have a couple of hours in a Comanche 180. It seemed a bit
underpowered. But it's book speeds are impressive, and it flies very
efficiently. Make sure its useful load will match your mission profiles.

--
-Elliott Drucker