You need to buy one copy of each for the fair use to apply.
toomuchtodo
Let everyone donate their DVDs and other physical media. You don’t need to buy it, you just need to possess the media.
veggieroll
Indeed, I forsee a "training dataset consortium" arising out of this, whereby a bunch of companies team up to buy one copy of everything and then share it for training amongst themselves (ex. by reselling the entire library to each other for $1).