thats a relative question and you will get a variety of answers. For a 15 size plane I have seen the price from $35-$50. I have the Lanier Shrike 15 kit and paid $35 for it. Just an idea

ExtremeFlightRC has just released a 15 sized 3D ARF for $89. You can see it here: [link=http://www.extremeflightrc.com/product_html/Mini3D.htm]Mini 3D[/link]



You also might want to post this in the KITS section. Also for maximum benefit consider testing it with a electric motor and sell it as an E-plane, the ezone.com has a huge community thats active and im sure you could get a response from them on this well

good luck


matt