https://www.reuters.com/article/us-tesla-batteryday/teslas-value-drops-50-billion-as-musks-promised-cheaper-battery-3-years-away-idUSKCN26D19P >Investors slashed $50 billion from Tesla Inc's market value on Tuesday despite CEO Elon Musk's promise to cut electric vehicle costs so radically that a $25,000 car that drives itself will be possible, but not for at least three years.