Grading costs money and takes time, so it usually only makes sense for cards already likely to be valuable based on rarity and condition
Myriad listings for ex Pokmon and 1 Star, alternate art cards, the two rarest available to trade, are listed on eBay, each with varying price tags
Slime Against Humanity isn't put into your graveyard until after it finishes resolving, so it doesn't count itself for its own effect
Sorry for the massive image
Apart from being solid, on-tribe creatures, Regal Leosaur, Cubwarden, and Snapdax, Apex of the Hunt offer some sneaky extra upside by allowing us to (essentially) have extra copies of powerful legends like Rin and Seri, Inseparable or Kaheera, the Orphanguard on the battlefield by mutating on top of them to change the name