December was a solid month for American automakers. General Motors Company (GM) had its best December sales month since 2007, with sales up 19.3% over last year. Full-year sales were up a respectable 5.3%. Ford Motor Company (F) had its best December since 2005, though its full-year growth numbers were actually down slightly due to, among other things, retooling to make way for its new aluminum-body F-150.

Even better, after years of haggling, Americans are paying up for their cars again. December had the highest average transaction prices on record, according to Kelley Blue Book, at $34,367.

So, what's the story here? Are auto stocks a buy?

I would argue that they are, but not necessarily for the reasons you see in the media.

To start, auto stocks didn't react particularly well to the sales data. GM stock was followed the broader market lower, and Ford stock dropped by more than 3%. Wall Street doesn't seem to be buying the argument that lower gas prices will automatically mean a sustained run in strong auto sales.

I agree. Consumer behavior doesn't change on a dime, and in any event wage growth has been sluggish since 2008, roughly keeping pace with inflation (see chart). The average American is in better financial health than they were, say, five years ago. But they're not exactly in great shape.

Furthermore, Americans– and particularly younger Americans– drive less than they used to and are more likely to share rides or use public transportation.

So, if I'm somewhat down on the macro picture for the auto industry…why am I bullish on auto stocks?

I'll give you three reasons: valuation, dividends, and guru purchases.

Let's start with valuation. In an overpriced U.S. stock market, auto stocks are one of the last subsectors to find real bargains. GM trades for just 8 times expected 2015 earnings. That's half the forward P/E of the S&P 500. Likewise, Ford trades for just 9 times expected 2015 earnings.