Yeah, no.
I understand your perspective, but the way I see it, it’s like renting a movie at home versus seeing it in a theater. For some people, the extra money to go to a theater is worth it. I’m not paying $20+ to see a movie once at home though, and especially not to see it on my phone. Discounted price for a discounted experience. If they want to charge $20 for the mobile version, and $40 for MacOS, then I’d be way more likely to try a triple-A game on a phone.
But you get it with no compromises on MacOS, so why would they discount the price there? This is buy once, play “anywhere” (anywhere that’s good for Apple). You don’t pay less for a game you only play on a Steam Deck either.
Sure, then $20 for the mobile app, and $60 for MacOS (which should include a mobile copy). That would work for me too. I don’t have a Steam Deck, but I for sure would not pay full price for a game just to play on the Steam Deck.
I think the Switch and the Steam Deck have shown that portable games are worth every bit as much as non-portable, but in both of these cases, they output easily to the larger experience at home. I think Apple is providing that too. $60 still makes sense to me, since you’re always buying the MacOS version which includes a mobile copy, which you said was acceptable.
