If you've been monitoring Rivian Automotive (RIVN -2.50%) stock over the last few months, you may think your chance to buy has come and gone. Since hitting multi-month lows last November, shares have spiked in value by more than 30%. But the chart below proves why shares are still a screaming buy over the long term.

Rivian stock is cheap compared to Tesla and Lucid Group

Rivian had a tough 2024. Sales grew year over year, but just barely. The company shipped 51,579 vehicles in 2024 versus 49,476 in 2023. Deliveries are still headed in the right direction, but these are not the growth rates that investors have gotten used to in recent years. Fortunately, Rivian is not alone. Tesla saw sales fall by 1.1% in 2024, its first decline in nearly 15 years. Lucid Group, meanwhile, saw sales jump by 71%, reaching new records thanks to new model introductions.

Looking beyond last year's results, Rivian has a promising future. In 2026, the EV maker plans to release three new mass-market vehicles: the R2, R3, and R3X. All should cost less than $50,000 -- a huge deal when it comes to tapping the largest section of the car-buying market. When Tesla introduced its affordable Model Y and Model 3 variants, sales growth picked up considerably. The same could be true for Rivian when its new models hit the streets.

RIVN Revenue (TTM) data by YCharts

You wouldn't know that Rivian has a bright few years ahead, judging by its price-to-sales ratio. Lucid Group trades at more than three times Rivian's valuation, while Tesla trades at more than five times its multiple. Lucid's premium valuation makes sense, given its high sales growth and diminutive size. But as you can see in the chart above, Rivian still has plenty of room to grow, even if its next leg of growth won't occur until 2026.

You'll need to remain patient for a year or two, but Rivian stock clearly isn't expensive if you can appreciate the likely sales ramp that will occur in 2026 and beyond.