Wine theft from high-end estates does happen fairly regularly - there've been organized raids on Bordeaux châteaux, Tuscan vineyards, and California cellars over the years. The tricky thing here is that the figure you're citing (€5 million exactly) might be getting mixed up with a different incident, or the details could be inflated in retellings. Without a specific winery name or date, it's hard to track down whether this was an actual coordinated theft, inside job, or something that got exaggerated in the telling. If you can narrow down which winery or when this supposedly happened, that'd help verify whether it's a real heist or maybe a conflated version of a few different wine crimes.