The massive valuations of electric vehicle start-ups such as Rivian, which made its public debut Wednesday on the Nasdaq at a higher stock price and market cap than General Motors, shows the legacy automaker is "so undervalued," GM CEO Mary Barra said Wednesday. Rivian's stock began trading at $106.75 a share, a roughly 37% pop from its IPO price of $78 a share and a market valuation of $91 billion. That compares with GM at $60 a share and a market cap of $86.4 billion. "What it highlights to me is the huge opportunity.