If you are looking for an exciting mid-range 5-color deck I suggest giving Tiamat a Try!
As for the high-cost tier, theres the 6-cost Mushu (Your Worst Nightmare) is a brilliant addition, as whenever you play another character, he gives them Rush, Reckless, and Evasive during that turn, and thats on top of his 2 Quest on his own
Most expensive Magic: The Gathering cards Foil Intuition (Judge Promos) Mox Jet (Alpha) Mox Sapphire (Beta) Timetwister (Alpha) Mox Emerald (Alpha) Underground Sea (Alpha) Time Walk (Alpha) Volcanic Island (Beta) Ancestral Recall (Alpha) Mox Ruby (Alpha) Black Lotus (Beta) Copy Artifact (Beta) Lord of the Pit (Alpha) Mind Twist (Beta) Black Lotus There are plenty of people who put big money into MTG, and its caused some spectacular prices throughout the years thanks to things like the Reserved List
The comparison that comes to mind is Helm of the Ghastlord spike thanks to Y'shtola, Night Blessed
Not one, but all of the cards
Dragons like Utvara Hellkite were designed to make a splash when they were cast, and this one definitely delivers