Lucid Motors (LCID -0.33%) stock looks expensive according to several traditional valuation metrics. Its price-to-sales ratio, for example, is 9.6. That's significantly higher than other electric car stocks like Rivian, which has a price-to-sales ratio of just 3.0.

But there's one factor that Lucid Motors has that Rivian does not. Even the likes of Tesla can't match this feat -- a feat that could actually make Lucid stock a bargain.

Lucid Motors stock is cheap, according to this metric

There are many reasons why a company might have a high price-to-sales ratio. The most popular reason is that sales are skyrocketing.

That's arguably the case for Lucid right now. Last quarter, its sales growth easily exceeded the rates posted by both Rivian and Tesla. Rivian actually saw its sales growth go negative last quarter -- a big reason for its discounted valuation.

Looking ahead, analysts expect Lucid to grow sales by 118% in 2025 following the launch of its Gravity SUV. Tesla, meanwhile, is expected to grow sales by just 16.6%, while Rivian's sales are projected to jump by just 11.6%.

RIVN Operating Revenue (Quarterly YoY Growth) data by YCharts.

To be sure, there's a long road ahead for Lucid. But if the company does grow sales by 118% this year, shares trade at roughly 4 times forward sales. That is based on next year's projected sales.

That's significantly cheaper than Tesla, and not too much higher than where Rivian shares trade today. So while shares look expensive on paper, rapid growth rates more than justify the valuation. Whether Lucid can sustain these growth rates over the long term is another question. But Lucid stock isn't nearly as expensive as its current price-to-sales ratio suggests.