Plus, instead of mere power, you can grab a creature that has a useful ability, from fetching up lands and tapping mana to drawing cards and destroying another permanent
The scry mechanic also works great if you can get the card to the top as well
This shapes the gameplay as you have to plan ahead, knowing that your summons (and your opponents) wont be around forever
Regular Creatures, Sorceries, Enchantments, and more can only be played during their owners turn, but Instants can be cast whenever their owner chooses
While these ones only have you rolling d6s, cards like Comet, Stellar Pup and Attempted Murder will let you roll a LOT of them
Over time, these different prices should equalize somewhat, even if they never completely converge