I am not sure but maybe it's possible that being a bigger company with more experience in hardware and possibly closer partnerships with other companies that Nintendo can match Steam Deck's specs for a lower cost, especially since there's a few things they can shave off the cost like designing for trackpads and extra buttons. Plus, Steam Deck was originally slated for a late 2021 release date, so if Nintendo launches Switch 2 sometime in 2024 I'd imagine the cost being a bit lower now.
As for price, Nintendo charges $350 for their Switch OLED, so they might be comfortable with a base price around that much for their next system.
Maybe I'm being too optimistic, but I'd really like Switch 2 to be close in power to the Steam Deck, even if they have to make some concessions somewhere to get there.