MLB.com

Do I get a refund for releasing a player?

It depends.  Although the player is no longer on your team, your payroll is still responsible for his salary just as a major league team is still liable for paying the guaranteed contract of a player it releases.  The only way you will get a salary refund is if another team claims your released player in the free agent pool. When another team picks up one of your ex-players, you are automatically refunded the amount that they are paying of his new salary.