The stock does seem a bit overvalued currently and I wouldn't be surprised to see some drops in the coming weeks. But regardless, $500 within 3 years. Mark my words.
And what valuation model are you using to arrive at this price? It seems odd that you consider it overpriced now, when the growth in the future that you're attributing to the Gen 3 is already priced in.
TSLA is great, and changed the auto game. But people are seriously underestimating the competition that is coming in the EV space, thanks to Tesla's success.
In this case I'd expect that he is also suggesting that he believes the stock to be overvalued on typical ways to evaluate stock but from what he believes the company will actually accomplish he thinks the value is higher.
But if you're certain it will be $500 in three years, you need some serious risk aversion (~2500bps) to think it's not worth buying it now at $250.
In other words, by saying it will grow to $500 you're expressing your view on value; this value is higher than price, so stock is undervalued.
How many people do you think can afford a ~$100k vehicle?