Tesla Motors (NASDAQ:TSLA) has delivered an in-your-face to its naysayers with the announcement that the coming quarter will be its first foray into profitability. With a full earnings release not due until May, we only know that the company sold more Model S sedans than it projected. That wasn't enough to deter Mr. Market, though, as the stock skyrocketed to all-time highs on the news. What do we know about the state of the company, other than its profitable first quarter? Is now the time to get in on this auto-industry disruptor?

Pump the brakes
Though the message will probably fall on deaf ears, investors shouldn't rush in to Tesla solely because it had a profitable quarter. Yes, the company is growing its sales every quarter and pumping out more of its limited model lineup, with a-sold out backlog going many months forward. The thing is, though, there are many ways to reach a bottom line that's in the black -- and they don't all signal continued profitability going forward.

We know the company has made and sold twice as many cars as it did a year ago in its first full quarter of production. But one of the biggest hurdles for the company is its weekly production. It needs to get the manufacturing process down to the point where it can sell its cars for more than it costs to make them -- you know, real profitability. We don't know if it has done this yet, and investors should be careful not to take this impressive, though ultimately inconclusive, piece of information too seriously.

Stop whining
Tesla permabulls will probably say I'm trying to dampen a crucial milestone for the company -- but that's not my intention at all. I think Tesla is an incredible company that has accomplished unprecedented things in its relatively short lifespan. Elon Musk, in my opinion, may be the single most influential technologist of our time. My sole point here is that this quarter's profitability shouldn't be taken as a sign that Tesla is out of the weeds. It may be headed that way; we just don't yet know.

Foolish bottom line
Regardless of Tesla's growth prospects, the valuation remains far too high to warrant any fundamentals-based investment. Since all trailing earnings are negative, let's use a sales basis for measurement. Tesla trades at a trailing price-to-sales ratio of more than 12. That number will, without doubt, come down in future quarters and years as the company continues to race toward scale. Still, it is far too much to pay given the downside risk -- not achieving scale, competition, and so on. For comparison, Ford (NYSE:F) trades at a price-to-sales of 0.38 and has a far, far more stable business to forecast. Cheaply valued and on the brink of a new product cycle, General Motors (NYSE:GM) trades at a ratio of 0.25. 

Tesla's valuation will trend down as the company's earnings catch up to market fervor, but a value-conscious investor couldn't invest in the company at today's price. 

Keep a close eye on coming earnings announcements, and make sure to focus on the company's manufacturing metrics. These will tell more about the future success of the company than any of today's financials.

Fool contributor Michael Lewis has no position in any stocks mentioned. The Motley Fool recommends Ford, General Motors, and Tesla Motors and owns shares of Ford and Tesla Motors. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.