I would say it isn't wrong to write/sell them, but it is for anyone to buy them. Which seems kind of contradictory.
It seems contradictory because it is
If you take money to write papers that other people will submit as their own work, you are conspiring with them to do something that is academically dishonest. That makes you wrong, too. Particularly since there is no legitimate purpose for which a person would write these papers for pay.