I don't agree. When you sell a built model, free download or purchased kit, you are seeking compensation for your time, labor and the cost of materials. I absolutely do not see an issue here.
You can disagree as much as you like Greg. It doesn't change the way the Law works.
Indeed you may only be seeking compensation for the work you have done. Legally you are entitled to do so. HOWEVER! You are using a model to do that work that was designed by someone else and earning money from it. You do not have a legal right to do that.
Look at it this way.... Lets say you were to manufacture a set of Star Wars Toys, from a kit that was available and sell them, and then claim that you were only seeking compensation for the work you did manufacturing them. That simply wouldn't stand up in Court, because you would still be in breach of the Copyright and patents and rights in the original design.
The Copyrights in the paper models allow for personal use only. They do not allow for commercial use, which is effectively exactly what you would be doing by selling them. Unless the designer or copyright owner specifically grants you legal release permission to do so.
As I said, A Pirate could sell a whole disk of commercial and free models claiming that he was only selling the work he had done in compiling them onto the disk. Do you think that he is entitled to payment for that work?? Do you think a Court would accept that as reasonable??
OK look at it another way.... You buy several CD's... You rip different tracks from them, and assemble them into a Compilation. Do you think it would be legal to charge for your time and materials in doing that? Of course not... and the same applies here.
But as I said, nobody is going to chase this down, because the cost of doing so would be too high with little prospect of recovering any money from it. Which brings it back to a question of your own personal moral choice.
Best Wishes,
Bspline (Copyright and Patents Lawyer)