You may well be onto something here... the model kit industry went into meltdown about 10 years ago as Boeing began hitting kit manufacturers for use of their IP - it was rumoured they were demanding up to $40 per kit to model one their planes
(the big debate was whether they owned the designs or not given they were typically built for the state and the state would often have several companies building any one plane - especially WWII designs or aircraft they built of other companies designs). However, Boeing won and most new western kit manufacturers now have printed on the box or instructions that the kit is officially licensed. Lockheed Martin also began imposing the same.
Coincidentally, the F-15, F-4 and Harrier (US Marine version) were all McDonnell Douglas products - and MD has since merged with Boeing. Similarly General Dynamics, producer of the F-16, sold their aerospace arm to Martin before they merged to become Lockheed Martin. Northrop and Grumman haven't sought licensing hence they can probably get away with the F-14 like design.
A cost of $40 doesn't seem to have eventuated - anecdotally, I'd suggest it's been about 10% but that's still a cost that they may not be willing to absorb or pass on...