This mono-red dyno rewards you with Dinosaur and Treasure tokens based on the types of the two cards that you exile from the top of your library on every upkeep
7 The Bridge Of Death Door To Nothingness The Bridge Of Death is a very funny card for decks that are all five colors, giving you a way to instantly make someone else lose the game
Wolfbriar Elemental is for the games where you have Primal Command but not much of a board presence so a Craterhoof Behemoth would not be enough to kill them
For a quick comparison, right now the showcase version of Gandalf the White is selling for over 30$, the foil showcase version is around 70$, and the normal version is listed at just shy of 20$
Ulamog is less flexible than the construct, but it gives us much more potential in a longer game so a single copy is certainly justified
(The exception on rarity are those serialized reprints of cards that are intentionally limited before printing)