(Bloomberg) -- A prominent Tesla Inc. investor on Wall Street warns his bullish case would be in jeopardy should Elon Musk abandon the long-held bid to bring a low-cost vehicle to the masses.Most Read from BloombergElon Wants His Money BackDubai Grinds to Standstill as Flooding Hits CityRecord Rainfall in Dubai? Blame Climate Change, Not Cloud SeedingSingapore Loses ‘World’s Best Airport’ Crown to QatarRed Lobster Considers Bankruptcy to Deal With Leases and Labor CostsAs the electric-vehicle ma