We show that online listing prices closely approximate transaction prices across Europe. Our validation uses the IWH European Real Estate Index (EREI), a near-real-time database of monthly purchase prices, rents, listing counts, and time on market for 1,154 NUTS-3 regions in 16 countries since April 2024. With publication lags as short as one month, validated listing prices offer a timely, comparable complement to official house price statistics. Purchase price levels correlate between 0.94 and 0.97 with transaction prices in the five most populous markets, while calibration slopes range from 0.95 to 1.00. Aggregate listing prices exceed benchmark transaction prices by 13% to 22%.