A few days ago, Jace, the Mind Sculptor and Stoneforge Mystic were banned by Wizards. What is unexpected is that the price for a Foil Jace is still high, close to $200. This may be because the are not many for sale, so their value remains high, or it may be a delayed effect of the banning, we will have to watch and see.
Jace is used in other formats, so his price may stay stable, but you can see both the Stoneforge Mystic and Foil Stoneforge Mystic are down since June 19th (46% and 30%, respectively)