It's a game. If you're unexperienced then you make mistakes, and place unexperienced bids. It is just like real life.
Market should be more on the free side not on the regulatory side.
Plus "above market rates" is a clumsy description. We all know, for example, players are much more expensive before playoff deadline, or beginning of new season. So it varies also on the moment of the season that you list your player. It's really superficial to say player X got bought for 1k and sold for 100k, it's just not enough information, and certainly not something you can easily and fairly regulate.
Not to mention you can buy a youngster mid season, train him(change his value completely) and sell him beginning of next season for more money. How would you even quantify that?