Short-sellers betting against Elon Musk's and Tesla found out that was just not a good idea this week:  They lost a collective US$1.5 Billion as the electric automaker had its best day in years.

Tesla shares were up more than 17 percent after the company reported a rare quarterly profit.  Most analysts had been expecting the company to post a $72 Million; instead, Tesla reported that it had turned a profit in the third quarter of $342 Million.

It's only the fourth time in the past five years that Tesla has reported a profitable quarter.  But after losing $600 Million in the first six months of the year, Tesla is expected to earn another $200 Million in the last three months of 2019, pulling off back-toback profitable quarters.

Tesla remains the most heavily shorted stock in the US, as well as the most heavily-shorted automaker in the world.  Even though shares are just shy of $300, they're still down 10.5 percent for the year.  And sales are still disappointing, down from the previous quarter and from the same quarter a year ago.