Hypothetically, why shouldnt a owner be allowed to sell a player? For the purposes of discussion, the sale of a player occurs where a owner recieves $1 dollar or more than the cost of the replacement player. In asking this question I am making two assumptions: 1) no newbies or trade raping is allowed, 2) the world is one that does not have many one-and-done type owners or requires a long term commitment. For those who will say it encourages tanking: imposes a minimum win requirement to stay in the world.
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Here is a few reason to allow the sale of players of prospects:
1) MLB, NBA, NFL all allow it.
2) Cash is an asset just like players and propsects
3) greater roster flexibility and trade flexibility
4) propsects can be put to there most productive use (I need a 3rd baseman and your real deep on AAAA type players, there is no FA of any MLB value. You value the cash more than I value the 3rd basemen available as FA).
5) its fun