Licensing fees are most likely why they need to be tied to real money purchases. The contract probably stipulates that a portion of money earned from the characters goes to the copyright holder. Since no money is earned from iridescent shards they're probably not allowed in the contract.
Are licensed characters ever going to be purchasable with Iridescent Shards?

How come all of the non-original characters cost Auric Cells? I also wouldn't even mind if they costed more than normal characters, but I'm also curious as to why we need to purchase them with real money.
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Because it costed/costs them more money to make / release than the original characters. (may actually be a stipulation of the licensing honestly) Alongside the normal 'creation/tuning' they have to pay license fees.
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Short answer is no. There have been rumors about a Nightmare edition which would include every dlc, but that's still not confirmed. Either way you'll be paying real money for them.
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Licensing fees are most likely why they need to be tied to real money purchases. The contract probably stipulates that a portion of money earned from the characters goes to the copyright holder. Since no money is earned from iridescent shards they're probably not allowed in the contract.
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Basically this. They can give their own characters away for free, but not other people's. This is the same reason why auric cells are unobtainable without paying real money.
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