Tesla shares were limping along around $200 in May 2019, about where they had traded five years earlier, when Elon Musk’s biggest Wall Street booster tried a gutsy experiment. Cathie Wood and her Ark Investment Management were already well-known for their way-out-there predictions that Tesla would build a fleet of robo-taxis worth $1 trillion and that its shares would soar 20- or 30-fold by 2023. Now she stirred the pot again by publishing online Ark’s new bull’s-case valuation of $1.4 trillion, implying a share price above $6,000, complete with every Excel calculation and assumption behind those estimates.