I don't recall Sony struggling to produce enough PS2's to ship in it's launch year. You are completely missing the point that to focus on pushing PS4 sales at this moment in time would take resources away from manufacturing PS5's at a time when they are already having trouble manufacturing PS5's as it is.
Sony is veteran in this game, and they can do it.. if they want to.. however obviously they don't ..
They have been through enough console generations and cases with low price and high price consoles at the same time to be able to maintain situation like this
It's not the year 2000 anymore. The margins on hardware are razor thin. The end of lifespan price cuts that you are longing for don't exist anymore, and haven't in over a decade. There's no reason to push the old tech at dirt cheap prices, when the only people you will be bringing into the ecosystem will be buying years old software from the bargain bin, or worse yet for the manufacturer, used games. Where there is little profit to be made, there is little incentive for a business to do it.