Like Wonder Picks, low-rarity cards will be cheaper, while higher-rarity cards will cost more
As design philosophy has changed and they have added more value to cards (including lands), card advantage has become less of a constraint, and being constrained as mana has become the games core constraint
Even with close to 20 years of power creep and shifts in Magic design against them, Ninjas are still an iconic and popular creature type, with a huge number of players maintaining Ninja tribal decks to this day
Where did they get it from
First, have Tidewater Minion, Illusionist's Bracers, and mana sources that produce the colours you want out on the battlefield
There's a 12.5% chance you'll get a mythic rare, and the wildcards mean you could end up bagging multiple rares