For seven total converted mana it seems reasonable, but what makes this card so powerful is its inclusion of the Miracle mechanic
A lot of balance and care goes into choosing the cost of a card, more than I can express here, but looking for similar effects on existing Magic cards can give you an idea of a fair costfor example, a ramp spell that puts two lands into play ought to cost 4 mana, per Explosive Vegetation
One mana becomes three immediately, letting you jump turns ahead
$92.00 Out of stock
I couldnt settle for just Selesnya (green-white) to match Yuna because Rydia, Summoner of Mist, and Terra, Magical Adept complement her abilities so well in Gruul (red-green) so I had to branch out into Naya (red-green-white)
Alternate win conditions like Promising Stairs add a fun challenge to gameplay