Reasons to NEVER SELL CHAMPS....
Here is what you lose when you sell a champ...
1) The champ itself
2) A PHC, 3*, or 4* crystal depending on what you are selling and what you got that champ from
3) At least 1 dupe reward pack (shards, sig levels, iso, and gold)... this multiples by however many duplicate levels you had on the champ you have just sold
4) A max signature stone. Since it will take at least one more duping to achieve max signature ability that's another loss here. ***(if you choose to use signature stones to fill this gap, those would be your loss instead of the max sig crystal)
So now that you see all of this... is it worth it? Patience is a virtue