What happened

One day after getting a boost from a positive analyst note out of Jefferies & Co., shares of Tesla (TSLA 2.92%) are revving once again, up 4% in 3:30 p.m. EDT Thursday trading.

With no new news about Tesla per se out on the wires, today, I think you have to credit today's stock price explosion to new Tesla rival Xpeng (XPEV -1.47%).

Rising red stock arrow representing a stock going up drawn on a yellow background.

Image source: Getty Images.

So what

Xpeng, as my Foolish colleague John Rosevear explained today, is the newest IPO in the electric-cars space, having just raised $1.5 billion selling 100 million American depositary shares (ADSs) at $15 apiece on the NYSE -- a result that Barron's calls "really, really" good.  

Now what

And here's the thing: Xpeng won this valuation despite having no profits whatsoever. (To the contrary, John says Xpeng lost about half-a-billion dollars last year and is continuing to lose about $200 million every six months today). Yet despite this lack of profits, S&P Global Market Intelligence puts the Chinese electric-vehicle maker's valuation at a cool $10.2 billion -- or about 34 times trailing-12-month sales of $303.5 million.

Now, if Xpeng is worth 34 times sales without profits, but Tesla shares are selling for less than 15 times sales with profits, does this perhaps mean that, despite a market valuation now approaching $420 billion, Tesla stock is actually still undervalued?

That seems to be the thinking on Wall Street today, which would explain why Tesla stock is still going up.