Sure, some of them are better than others, but they have been relatively balanced (especially over the past few years)
So, no you cant convoke and sac creatures for mana to pay for this
The value here is pretty high in reprints, but many of the new cards are narrow
2 Captain Hook, Forceful Duelist D23 Promos - $1,300.00 One of the most memorable villains from classic Disney films, Captain Hook has staked his claim as one of the most valuable cards in the game, particularly the D23 promo of the card
Thing in the Ice is one of the few defender creatures that doesnt need external help to end the game
Hurloon Minotaur (2): This card isnt worth much nowadays, oddly enough