Firstly: Why are we judging the value of a game based on numbers? Should it not be the case that a game's price is justified by its gameplay loop? I don't care if a game features 200 race tracks if the game itself is far inferior to the one which features 40. Play the game yourself before going off on a several-year-long crusade.

But even then, if I were to play ball with you: Explain how MKWorld has less content than MK8DX, because while MKWorld has 40 tracks (16 original, 14 returning, and 10 new tracks were added with the latest update) compared to MK8DX's 96, it is simply the case that MKWorld has a larger roster (50 versus 48), MKWorld retains all the Grand Prix & Time Trial modes from MK8DX, MKWorld includes an open world to roam around and complete hundreds of mini-game objectives in (whereas MK8DX features no unique single-player experience), the soundtrack from MKWorld is vastly expanded upon with far more original (and, I'd argue, much higher quality) music than that of MK8DX, and introduces a complete overhaul on the traditional MarioKart gameplay loop, allowing for an entirely new dimension of gameplay via parkour mechanics (whereas MK8DX follows directly in line with all preceding entries of the franchise besides the new coin and anti-gravity mechanics). Additionally, I don't see how the roster of MK8DX (with all the Koopalings, Pink Gold Peach, baby characters, and so forth) is any better than MKWorld (which features an entirely original cast of characters, though with some wacky/wild inclusions like the Baby Penguin from Mario 64 lol).

This in addition to a much stronger graphical and technical (4K, consistent 60FPS) performance, I cannot see how you could argue MK8DX justifies its price tag over MKWorld, especially when I've included all the Booster Course content in this comparison. That's an $85USD MK8DX going against an $80USD MKWorld which is still recieving free updates to this day.

Edit- Also, Bob-Omb Blast is in MKWorld.

It is? Since when?

And weren't the new courses already part of the overworld and Nintendo just made them playable?