Amazon, Inc. (NASDAQ: AMZN)-backed EV startup Rivian confirmed Friday it has confidentially filed for an initial public offering that reportedly could value the company as much as $80 billion. The company's eye-popping proposed IPO valuation has elicited mixed reaction from investors.

Rivian is developing two EVs – R1T, a pickup truck, and R1S, an SUV. Tesla, Inc. (NASDAQ: TSLA)'s Cybertruck, which is in the works, will be up against Rivian's R1T. Tesla CEO Elon Musk had an interesting take on Rivian's proposed valuation when a Twitter user commented on it. 

Musk replied Rivian should have delivered at least one vehicle per billion of its valuation before its IPOs.

Don’t want to be unreasonable, but maybe they should be required to deliver at least one vehicle per billion dollars of valuation *before* the IPO?

— Elon Musk (@elonmusk) August 28, 2021

Musk's response may have some merit. At an $80 billion valuation, Rivian will have a market cap higher than legacy automakers such as General Motors Corp (GM), Ford Motor Co. (F) and Stellantis N.V. (STLA) as well as hot Chinese EV startup Nio, Inc. (NIO). But at least Rivian's delivery timeframe for its RIT pickup truck is ahead of Tesla. The company is planning to deliver its R1T pickup truck in September, potentially becoming the first to market.

Lordstown Motors Corp. (RIDE) is planning to begin limited production of a rival product named Endurance next week. Tesla, Inc.'s Cybertruck and Ford's F-150 are not expected until next year.