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When Kevin Zraly first started studying wines almost 50 years ago, it wasn't the most popular alcoholic beverage in the U.S. "People looked at me like I was nuts studying wines," Zraly said. "All my friends were drinking beer." At 21, Zraly hitchhiked to California to get exposure to the wines there. And after graduating from college, he took off for Europe. By the time Zraly was 25, he was hired by restaurateur Joe Baum. The role took him to Windows on the World restaurant at the top of the World Trade Center. Zraly worked there until the terrorist attacks on Sept. 11, 2001. At the time, the restaurant reportedly had the largest wine sales of any restaurant in the world. The eatery served as the inspiration for Zraly's wine course and corresponding book, "Windows on the World Complete Wine Course." Today, Zraly still teaches beginning, intermediate and advanced wine students. And his book, which is updated every year, is one of the top-selling wine books in the world. Over Zraly's career, consumers' attitudes toward wine have changed. The U.S. is now the number one global consumer of wine. And millennials are now the number one consumers, followed by baby boomers. What's more, U.S. wine consumption has continually gone up in the past 25 years, Zraly said.

Kevin Zraly, wine educator and author Source: Kevin Zraly

That goes even for the financial crisis of 2008-2009, which only helped to change the pattern of wine consumption, Zraly observed. "People didn't have the same disposable income that they had, and then they realized, 'I don't have to spend $50 on a bottle of wine. Look at what I'm buying now, and it's just as good,'" Zraly said. Now, it is possible to get great wines for $30 a bottle, and the sweet spot for wine right now is $15 to $20 a bottle, according to Zraly. In fact, he lists 700 wines that are under $30 a bottle in the back of the latest edition of his "Windows on the World" book. "You don't have to spend a lot of money to get a good bottle of wine," he said. But you are more likely to get better quality for the value if you choose certain kinds of wine. Here are the wines that Zraly said have the most for your money.

Prosecco

Prosecco is a sparkling white wine from Italy that Zraly said has endeared itself to consumers partly for one reason: It's easily pronounceable. Another attractive feature: You can get most Proseccos for $15 or under. "What it's doing is cutting big time into the Champagne market," Zraly said. "Champagne is at least double the price."

Pinot Grigio

Another popular white wine is Pinot Grigio. It comes from a grape variety that can grow around the world, but Italy and France have really developed it, Zraly said. "You can get a good Pinot Grigio at $15 a bottle, between $15 to $20 a bottle," Zraly said.

Rosé

Rosé, a pink wine, has seen a surge in popularity. And while there have been surges in interest in rosé in the past — including for sparkling wine or Champagne — this time, it looks like it's here to stay. "Rosé was cyclical: 'It's summertime, let's have a rosé,'" Zraly said. "But not anymore; it's not like it's just a trend right now." When it comes to price, color and taste, the best rosé wines come from Provence, in France, Zraly said.

Malbec

Malbec, a full red wine, can be grown around the world. But Argentinians own this particular grape. That's because the Mendoza region of Argentina has the perfect land to grow these grapes. At the same time, the land there is dramatically cheaper than other wine-growing regions, such as Napa Valley. The result is a quality wine that's not too expensive, Zraly said. "No one grows as much Malbec as Argentina, not even close," Zraly said. "And there's so many of them that are under $20 a bottle."

Rosso di Montalcino

A great wine that comes from the Tuscany region of Italy is called Brunello di Montalcino. It's one of the best wines in the world, according to Zraly, and it's also one of the most expensive. But Rosso di Montalcino, another type of wine, is made from grapes from the same vineyards. And because they use younger vines or other variations, the wine is one-third the cost, Zraly said.

Beaujolais

Another area that produces quality red wines is the Beaujolais region in France. There are three levels of Beaujolais — basic Beaujolais; Beaujolais Villages, which come from the villages surrounding the Beaujolais district in Burgundy; and Beaujolais Cru, which also comes from certain villages within the same area. Basic Beaujolais has the lowest cost, typically $20 or less, while Cru is the most expensive.

Côtes du Rhône

Cabernet Sauvignon