Mario Kart 8 Deluxe is $60; I don't think it's correct to add the DLC price to that.
Also Deluxe is improved in a number of ways: new characters, new battle mode with 8 new courses, two items at once, smart steering, etc. And it supports 12 players in LAN mode (though MK World supports up to 24!)
Super Smash Bros Ultimate is also significantly improved vs. its Wii U incarnation (its roster includes basically every character from the series - hence "ultimate"), and is also $60 (though DLC will almost double that if you want everything.)
They are both fantastic games that you can basically play forever. The Wii U games were also great - but the Switch versions are even better.
Historically Nintendo game cartridges were expensive than disc-based games for PlayStation etc., but these game cards at least are still $60 - same price as the Wii U disc versions (and the Wii U game prices are equivalent to $84+ in 2026 dollars.)
Nintendo's deal is that the consoles are platforms for their outstanding games, and first-party exclusives are the biggest reason to buy a Nintendo console (though they are also great handheld systems and support local multiplayer gaming without an internet connection.)