The long-term thesis Model S demand may be strong, but after Wednesday's after-hours surge, Tesla Motors Inc (NASDAQ:TSLA) has an $8 billion market cap. Meanwhile, General Motors Company (NYSE:GM), which — along with its joint venture partners — sold 9.3 million vehicles last year, is worth just $44 billion. Does Tesla, which has one relatively low-volume product, deserve to be in the same "market-cap league" as a global automaker like GM?