No single piece in either of the aircraft kits is anywhere near as complicated as the one-piece Charger body. The airplane wings, and even the fuselage halves, are molded using relatively simple tooling compared to what is needed for a one-piece car body.
^ This guy gets it.
Cost and flexibility are only two of MANY issue when making a clear body kit. Please note that none of the more recent kits are near the size of the Petty Charger, not near the age of the Petty mold......that has been modified a number of times. I have two friends in the industrial molding industry......both talk about how hard it would be to get a mold the size of the Petty kit to come out correct EVERY time.....which is what is required in mass production. Ten percent rejects would have raised the cost a bunch.
^ Him, too.
I can see (pun intended) both sides of the clear body argument, and there's no right answer. Some like to be able to "see through" the body and look at the chassis details, which are usually hidden from view with an opaque body. If you're going to build an accurate replica, however, the body will be painted, so the "clear body" selling point is of no value.
Buy it, build it, or catch the bus back to 1971 and buy an original kit for $6.99.