It’s not the cost, it’s manufacturing capacity and supply.
Theres only so many discs that can me manufactured in a day, they also need to supply movies and the blanks markets.
They have hundreds of other games to print. So yeah they make 500k discs a month ahead of time, and if Walmart gets 20k they have 10k stores, that means each store is getting a whooping 2 units.
Did you miss the part of my comment where I specified that my information was from when digital was non existent….?