I just did a search for players over 10 million listed on the transfer market and there were about 15 players. Now I don't know why they are listed for that price, but I'm sure they have their reasons. If they are legitimate reasons, then this tax would stop them doing this. (Again I don't know why they do it so I can't give the reason).
I agree that people should take care when listing their price. However, new players might not know the right price to list a player, so might list very high prices initially and be taxed a lot of money and will probably plead ignorance about the tax.
I can't remember the rookies height but his skills were fairly good. There might have been better players than him on the transfer list, but all I'm saying is that I think he is worth a lot more than 20k, and there was no way I was going to let him get sold for 20k.
You say buying your own player back is even worse than paying tax for noone buying him, but that wasn't an option for me. I listed the rookie at 1k, at the deadline he was at a price that I considered far below his true value, and so I was happy to lose a thousand or 2 to buy the player back. Paying tax is only relevant if there is no bid on him.