I’ve read several posts where players are delaying championing a character with 13 covers and selling off their covers instead. I don’t understand why you would waste that farming opportunity. Is it only about trying to avoid the dreaded scaling problem or something?
Signed,
D.U.H. (Don’t Understand Heroing) 
Because most people don’t have enough iso to champion all characters so they have to be selective. You don’t want to champ Venom and then not have the iso to champ Teen Jean or Red Hulk.
I guess I never have that many waiting to be champed at the same time. Perhaps that is a new problem I will be encountering as I build my 4* roster (Just starting, no heroes with more than 6 covers). How much is it to champ a 4* once they’ve capped?
From level 120, a 4 star costs a little under 400,000 iso to champ. I have 8 fours at thirteen covers. Of those, 3 covers in my RQ could be applied to potential champ levels. Only can currently champ one before those covers expire.
So yeah, sometimes you might have sell off a 13th cover when you know you can’t champ them within 15 days or if they’re just characters that won’t help you much even when champed.
Also, farming is less valuable than actual usefulness in game. When you’re at under 10 champed 4s, quality is more important than quantity.