For more details about the program, check the kids corner schedule
Since 2020, these promo cards have consistently sold at auction for over $24,000, with the highest sale to date at $50,000 (Source)
I'd guess Dimir and Golgari midrange are likely to be the new flavor of the month, unless there's some really good new cards in Bloomburrow
If you're just interested in owning this card in the unlimited edition, you can pick up a damaged copy for $80, but setting your sights on a first edition copy will cost upwards of $400 if you find one in better than LP condition, though more sales data is needed to determine the exact amount
Marketplace TCGplayer Sets Marketplace Cardmarket Sets Market Trend Price History Deck Usage & Meta Stats Public deck and tournament usage for Ice Doll Mirror
Some of them were so compelling and popular that they formed the foundation for future card designs in tournament-legal sets