Concerning law... in this case copyright law... P81 can design his own ships and sell them for a profit. No problem there. It only becomes a problem when he takes a copyrighted design, in this case the Enterprise from Star Trek (owned by Paramount Pictures), makes a model of it based on that design and which is automatically identified as, in this case, said Enterprise, and then asks people to pay him for it. By doing this, he is making money out of someone else's design, regardless of how much work he has put in it. Without a licence from Paramount to do so, P81 is committing a felony--if indeed he is asking money for his Enterprise model.
As I said, these problems would not exist had he designed something original, which didn't exist yet, and then asked money for it.
An example might clarify this, as some people here obviously have a problem understanding this. Take, for instance, a novel that you've written. It is entirely original: you came up with the story, the characters, and so on. All typed on your trusty computer. Now you want to make money of it, as is your right, by publishing it. You do that, and a few months down the line you happen across a website that is selling your novel. You recognise it instantly. This guy has ripped off your book and is selling it at a profit, without asking you, let alone cutting you in. Enraged, you e-mail him, and he replies dryly that he can do whatever he wants since, after all, he copied the novel by hand, using a quill and writing it on parchment. That was a lot of work, and he deserves to be paid, right? Wrong--it's not called "copyright" for nothing--only the original maker of a work owns the copyright of said work, i.e. the right to publish the thing at a time of his choosing, or to have it published. Authors retain inalienable rights, and no one is allowed to make money off of someone else's work, no matter how much effort went into the copies or derivative works based on the original.