The argument is flawed, for though digital copies of new games are rarely discounted on platforms like the PS Store, physical copies are often sold at a reduced price at brick-and-mortar stores.
Why is it flawed? Physical price is often cheaper, used or new. You can buy in different marketplaces (imports) and then can be resold if desired. I suppose it’s possible to buy from different digital marketplaces, but may not be straightforward on some platforms.