It's not a surprise that this rare card is more expensive than most mythic rares in Dominaria. Shalai is the ultimate protector! In addition to her incredible abilities, Shalai is also an angel, which makes her a perfect partner for Lyra Dawnguard.
Together these two cards can create an angel tribal deck so powerful that many staple decks in Standard will have no chance against it. But Shalai will work on her own as well.
Modern Burn decks will have no way of removing your creatures from the table, thus rendering them useless. If you're not on board with this card yet, then you should reconsider your values.
Most prices on these 11 cards will change, but others will stay where they are now. It's hard to predict which ones will grow in price, but you can always wait for the Pro Tour Dominaria and check the resulting prices afterwards. Stay tuned to GameSkinny for all things Magic: The Gathering!