But they are doing this all for what? Won't the market average out to the same unit price at the end of the day even if they can successfully create discriminatory spreads?
Think more in terms of behavioral psychology rather than idealized market dynamics which require rational actors and easily accessible information. Each corporation wants to optimize their customers' behavior for efficient extraction of wealth.
They want each customer effectively siloed in an ephemeral, eternal now: whatever the phone screen presents in this moment, and little else. The consumer may have a few scattered memories for context when presented with a potential purchase, but ideally isn't tracking prices or doing much research. The goal is to create those circumstances and (within them) reduce friction spending money as close as possible to zero.
Do that to as many customers as you can. Subvert their software and turn their own computers against them to achieve it. Instill learned helplessness and stimulus-response leading to purchase. Unit price and revenue will sort themselves out once you have a bunch of addled addicts staring at your shiny products in a digital environment you design and control.
That's the game. And that's why these companies will oppose arbitrage with all they can bring to bear, and fight with the brutal jealousy of gangs defending turf.
