Shares of Rivian Automotive (RIVN +0.49%) look startlingly cheap versus other electric vehicle (EV) stocks, like Tesla. Rivian trades at just 3.2 times sales; Tesla trades at more than 13 times sales.

If Rivian were valued like Tesla, there would be more than 300% in instant upside. Of course, that valuation gap won't be closed overnight. But there are two reasons to believe that Rivian stock should be worth considerably more than it is today.

1. Rivian is about to copy Tesla's playbook

At the end of 2019, and near the start of 2020, Tesla stock typically traded just above 3 times sales. That's right about where Rivian shares are today. But in March of 2020, something huge happened: Tesla began deliveries of the Model Y.

For Tesla, the importance of starting Model Y deliveries cannot be overstated. Today, more than 95% of its automotive sales come from just two models: the Model 3 and Model Y. And according to most estimates, Model Y sales account for the bulk of those combined sales figures.

It's likely, then, that a solid majority of Tesla's automotive sales hinge on the success of a single model: the Model Y. Last year, it was the best-selling vehicle in the world.

That vehicle arguably built the foundation for the company's $1.2 trillion valuation. Its success stemmed from multiple factors. But there are two factors in particular worth noting.

First, the Model Y debuted with a base price of less than $50,000. Most car buyers are trying to stay below that threshold for their next car purchase, so making the model affordable is crucial to achieving mass sales.

Second, the Model Y is not a sedan, it's a crossover. Hatchbacks with more interior space are increasingly more popular to consumers than sedans like the Model 3.

All this is what makes Rivian's upcoming launch of its R2 SUV so exciting. It's the company's first model priced under $50,000. And the vehicle's SUV form factor arguably has more consumer demand than crossovers (which are smaller), according to recent data.

Next month, R2 deliveries begin. And while it may take a few years to achieve peak sales volumes, this could be the start of the automaker's next major growth spurt.

Image source: Getty Images

2. This $10 trillion market could change everything

R2 sales are the nearest-term growth catalyst for Rivian. But there are also some other exciting long-term opportunities for the company.

The biggest is likely the robotaxi market. Some experts believe this market could eventually be worth $10 trillion globally.

Rivian's robotaxi opportunity is still in the very early innings. The company has stepped up AI investment significantly in the hope of achieving full autonomy in the coming years.

We already have early indications that other multibillion-dollar companies share Rivian's vision. Last month, Uber Technologies agreed to purchase up to 50,000 Rivian R2s to power its own robotaxi division.

I wouldn't bet on Rivian simply for the robotaxi potential. But at just 3.2 times sales, its stock looks too cheap to ignore when you factor in near-term R2 sales potential as well as the longer-term robotaxi opportunity.