True, but believe it or not, it's chump change for 40hp that'll crank a prop reliably on an airplane . Oh, and the gearbox is another $950 or thereabouts. you'll even pay a couple hundred for a prop.

Basically, take the cost of the r/c piece and add at least one 0 to the end - that's the cost of the equivalent in full scale .

I.e. take an R/C flat four 4 stroke like the O.S. at about $1700:
http://www.osengines.com/engines/osmg1320.html

add a zero and you're about at the equivalent in full scale (Rotax 912 series):

http://www.kodiakbs.com/engines/912ULS.htm

(actually this one is the 100 horse which is right at about $20,000 new)

When you get into complete planes, you need to add two 0's usually....

LS