Let's do a quick brand recognition check:

If I say, "Life takes ____. It's everywhere you want to be."

Chances are, you'll say "Visa."

If I say, "There are some things money can't buy. For everything else, there's _____."

Chances, are you'll say "MasterCard."

This sort of recognition doesn't come by accident. Visa (V 0.33%) and MasterCard (MA -0.07%) have plowed money into effective marketing campaigns over the years trying to edge each other out. While it's hard to call a winner, at the very least they've succeeded in entrenching themselves as an ultra wide moat duopoly in the payments space. Interbrand recently valued Visa's brand at a whopping $5.5 billion. MasterCard rings the register at $4.2 billion.

Visa and MasterCard have become so omnipresent that the idea that your average business won't accept one of them for payment isn't even entertained. Who really thinks twice about paying with a card these days? I mean it's just so darn easy.

When you mix equal parts strong brand with unconscious decision, the results are enough to make any investor drunk with enthusiasm.

Look no further than Altria for a case study in this equation of long-term value creation. The company has been one of the best-performing stocks over the last 50 years, propped up by its strong brand (Marlboro) and a product that gets bought and used as part of a generally unconscious habit.

Visa and MasterCard have carved moats so wide and so deep that they can still achieve a 13.6% and 38.1% return on capital, respectively. Their gross margins are nearly 100%, with both bringing home about 40% of their revenue as income. That's truly stunning for two companies with a combined market cap of $200 billion.

Both have wonderful businesses whereby each next swipe costs them virtually nothing extra to process because their networks are already built out. Not only that but both companies have long runways ahead. They can grow in an environment of flat or even negative GDP growth as people continue the long trend toward plastic (I couldn't tell you the last time I carried actual dollar bills), as well as expanding abroad. Eighty-five percent of the world's transactions are still completed with cash. Not only that, but since they take a slice of your swipe revenues should continue to rise along with any inflation instead of being crushed by it.

So after gushing affection for Visa and MasterCard, why do I sit admiringly on the sidelines?

All this greatness isn't exactly exclusive information. Mr. Market has bid Visa up to a steep 33 times earnings and MasterCard isn't far behind at 28 times.

This is the part where I should repeat Warren Buffett's well-known mantra to myself...

It's better to buy a great business at a fair price than a fair company at a great price. It's better to buy a great...

But I just can't convince myself that paying 30 times earnings for a $100 billion company is a good price. And don't even get me started on those paltry dividends.

At some point, the drag of being a company that large shows its face.

It doesn't help that as Visa and MasterCard grow larger so do the regulatory bull's-eyes on their backs. A federal judge recently struck down the 21-cent cap on interchange fees thinking the cap "runs completely afoul of the text, design and purpose." Basically, they were saying the fees were too damn high.

A new fee hasn't been proposed yet, but expect it to land closer to the 12 cents proposed by the Dodd-Frank Act.

While this will only apply to revenue earned domestically, the U.S. is still a cash cow market for both companies and a cap that low is a pretty hefty hit. 

I may very well sit around and watch both MasterCard and Visa operate wonderful businesses at lofty valuations forever because Mr. Market doesn't seem to want to let them come down to earth. I'm sure they'll both do very well in the future for all of the reasons outlined above, but at today's prices, so does everyone else.

Editor's note: A previous version of this article stated that Visa and MasterCard directly profit from interchange fees. The Fool regrets the error.