If you sell a 3-Star champion today, and then pull that same 3-Star from a crystal next week, you get a "new" champion instead of a "duplicate." You have just of the duplicate bonus. You get less Iso-8, less Gold, and zero shard progress.
In the vast universe of Marvel Contest of Champions (MCOC), your roster is your greatest weapon. Every player, from the fresh Summoner in the Proving Grounds to the veteran Paragon contender, eventually faces a universal question: What do I do with all these duplicate Champions? how to sell champions on marvel contest of champions