Our prices have updated! CardCastle now uses MTGStocks, who offer more accurate and reliable card price data.
MTGStocks has prices based on TCGPlayer and CardMarket, and is updated regularly. You can learn more about them and how the prices work here.
We are still working on an issue where certain foil cards that are printed in some supplementary products don't have a price listed and will only show the non-foil prices. We are aware of this error and are working to solve it as soon as possible.