Tesla stock has fallen more than 50 percent since December, plummeting to about $230 per share from a 52-week high of $488.54. Insiders and board members are among those dumping their stock amid one of the worst corporate losses on the S&P 500. "We struggle to think of anything analogous in the history of the automotive industry, in which a brand has lost so much value so quickly," JPMorgan said in a recent analyst note. Musk is even begging people not to sell their Tesla stock. (Trump's commerce secretary made similar pleas on TV recently, as well.)