Why is Yakuza 0 so expensive?

Just got Kiwami and have been playing through it. I love the game, and looking into getting 0 after I'm done.

Yakuza Kiwami steelbook was $39 brand new for me (Canadian). Yakuza 0 is showing up at $79 brand new. Isn't 0 older than Kiwami? What's with the pricing?

Sidenote: Is Yakuza 6 worth it after 0? Is it the same game play etc?

Edit: My lord guys, I'm not debating whether it's worth it or not. I'm asking why the fuck it's still $79 8 months after release. Even Horizon has hit $39 by now. I'll wait for a sale.