Warren Buffett is very selective about which companies he invests in. That's why investors should take note when he sticks by an investment for decades, even after the company grows immensely in value. Right now, one of Buffett's best stock picks is on sale. And so far, Buffett isn't selling a single share.

This is the perfect Buffett business

Buffett considers a wide variety of factors when deciding whether to invest in a particular business. One of the most important is what economists call an economic moat. An economic moat is a kind of competitive advantage that can endure for years, if not decades at a time.

When it comes to strong economic moats, few companies can match the power of Visa (NYSE: V). Just take a look at its market share figures. According to most metrics, Visa controls at least half of the U.S. credit card market. Just three companies -- Discover Financial Services, Mastercard, and American Express -- control the remainder. Suffice it to say that this is a highly consolidated market controlled by a handful of powerful competitors, Visa being by far the largest.

Merchants want to accept forms of payment that consumers can pay with. And consumers only want to carry around forms of payment that merchants will accept. It is this dynamic that has helped consolidate the payment industry in the U.S. -- a dynamic that only grows stronger over time. That's because Visa's dominant market share provides two critical benefits.

First, its network generates more data than its competitors combined considering more than half of credit transactions occur on its network. Second, Visa's business model is asset light, resulting in greater levels of profitability the more it scales. As the largest competitor, Visa can generate returns that the competition can't compete with. Over the last decade, Visa has dominated the competition when it comes to profitability, posting profit margins of nearly 55% last quarter.

With a strong market position supported by natural industry consolidation and the benefits of scale, Visa has accumulated an economic moat that most companies can only dream of.

Is it too late to buy Visa stock?

Buffett first bought Visa shares back in 2011 at a price point of roughly $40 per share. More than a decade later, shares trade above the $270 mark. Is it too late to get involved? Absolutely not. Shares trade at just 29 times earnings -- roughly what the S&P 500 index as a whole trades at. In a nutshell, you're able to buy a long-term Buffett stock with an incredible economic moat and profitability levels for zero premium versus the overall market.