Is it unethical to hire a paper writer AFTER the assignment is done? This is an intriguing scenario that came to my mind. I have not done this and am not planning on doing it, but I am curious about it. Of course, it’s well known that if you hire a paper writer to write your assignment for you, that’s cheating. But what about this situation?:

You have a difficult writing assignment. You follow all the rules, do it yourself, turn it in, and then you get your grade, and it’s a poor grade. But you want to learn what a really good paper for that assignment would look like, for the purposes of gaining knowledge, not grades. So you hire one of those paper writers people usually use to cheat, who is known for getting (dishonest, of course) As on all the papers they write, to nix it for you, so you’ll have an example of what an excellent paper would look like for your study pleasure.

So my question is: is this unethical, and if so, why, and what might be the consequences were it found out? The reason it seems interesting is because it’s being done after the assignment is turned in, so you’re not doing anything to deceive/defraud the teacher or get grades you did not merit – all transactions with the teacher were done by the book. But on the other hand you are going through the motions you’d go through to cheat, not to mention paying money to someone people pay to cheat. So where does this situation stand, ethically, and why?
In your hypothetical situation, no cheating occurs, since you do not misrepresent your own efforts. Comparing your own to someone else's solution after corrections have been returned in order to better your understanding is a perfectly good study practice.

Let me also clarify one point: you say, "paper writers [...] known for getting (dishonest, of course) "A"s on all the papers they write". There is nothing dishonest about the A grade. If the teacher gives it an A grade, it's because it is an excellent paper. If it had been handed in with a different name on it, it would have received the same honest A grade. The only dishonest thing is the student's behavior in putting their own name on it and claiming it as their own work, and arguably the ghostwriter's in knowingly assisting in this deception. Absent this, everything is above-board.

The only point where questions could be raised is the influence of money in your hypothetical. There are two places where this could play a role:

1) Acquiring this solution is expensive, and therefore out of reach for poorer students. This kind of disparity seems to be more acceptable to some societies than others, as shown e.g. by the price of education in the US (lots) vs Germany (nothing).

2) You are contributing to the maintenance of an industry which is predominantly assisting others' dishonesty. On this question, which is similar to e.g. contributing to bittorrent development because you like to use it to download linux distributions, I think that society has not formed a uniform opinion, and it is left to the individual to decide their own comfort level.