> “The essential problem … is what economists call ‘transaction costs,’” Goldstein wrote in an email to The Daily. “Millions of individual copyrighted works may be copied in the course of any training incident, and it’s simply impracticable for the platform to obtain licenses from the copyright owner of every — or, indeed, any — single work.”

Seems strange. The question should be whether you legally have to do so or not. If you do whether it is impractical or not is not a reason to break the law. Perhaps it makes your business not feasible but so be it. If you ran a clothing store that required you steal from other brands and remix it for your customers, you couldn't say "it's impractical for me to get permission", no?