It’s like the 1500ml water bottles that are next to the 1500ml Pepsi bottles. Beyond the cost of the plastic, water and filtration (pretty much the same bottle and filtered water that’s used to make Pepsi) there’s no fucking reason they should be the exact same price.
Games too. The digital download is exactly the same price as the physical. And these days there’s no reason to even get the physical anymore because the game isn’t actually on the disc. It’s just a script that opens the game store and downloads it.