Mike Jackson, the CEO of the U.S.’s largest car-dealership chain, described Tesla Motor’s (TSLA) market value as “inexplicable” following an investor surge that briefly propelled its valuation beyond that of General Motors (GM).
The AutoNation (AN) head made the comments during an interview at a New York automotive event on Tuesday. He argued that Tesla was overvalued while GM was undervalued, the Wall Street Journal reports.
Tesla stock could either pay off for investors or turn out to be “one of the great Ponzi schemes of all time,” he said, adding that competition from other automakers—who have invested billions in developing electric vehicles—would eventually lead to Tesla’s market value correction.
On Monday, Tesla was valued at $51.17 billion on the back of a surge in its stock price to $313.73 that allowed it to briefly surpass GM as the most valuable auto maker in the U.S. Last week, the Silicon Valley company’s market value overtook Ford Motor’s (F).
Tesla continues to be buoyed by investor confidence despite its luxury vehicle sales proving unprofitable and continued uncertainty over its ability to deliver the mass-market Model 3 at a price point of around $35,000, among other challenges.
Tesla did not immediately respond to Fortune‘s request for comment.