The shocking truth about mobile gaming

Some just want to annihilate the dragon. Some want to crush the candy so bad they'll shell out hard-earned cash to advance to the next level. Some will even spend thousands of real dollars to visit a virtual casino with no chance of a real, actual jackpot at the end.

This is the growing world of in-app purchases, or "micro transactions," a multibillion dollar industry based on "freemium," a category of smartphone apps that are free to download but users can pay real money to either continue using past a certain point or to advance in difficult or hard-to-beat levels.

Data suggest that iPhone users tend to spend more than Android users, and in general, the world of in-app purchases is no different. Those who choose Apple spend more on average in nearly all games that are supported on both platforms, according to data provided to CNBC by NPD Group's Checkout Tracking. Checkout Tracking studied the behavior of its users in the six-month period between December 2014 and May 2015.

The NPD system allows users to opt to have their purchase behavior tracked. NPD then uses the aggregated data for market research on consumer trends and behavior. With 2 million users distributed around the nation, Checkout Tracking has a pretty good representative sample of the habits of Americans on their smartphones.

The most popular games across the two platforms are pretty similar: "Clash of Clans" and "Candy Crush Saga" take the top spots on both systems.

But it's in terms of average in-app spend that iTunes and Google Play users distinguish themselves. The average spend for iPhone users on "Game of War—Fire Age" was $398 during the period studied, more than twice the $165 the average Android user spent.

Across all apps, iPhone users spend more on in-app purchases, too, $56.24, as opposed to $52.78 for Android users.

"The income levels are typically higher for Apple users," said Liam Callahan, a gaming industry analyst at Checkout Tracking. "It probably speaks more to the engagement on that platform."

Premium to freemium

The paid mobile gaming industry is broken into two categories: Premium games, for which users pay off the bat, and free-to-play (or "freemium"), which you can play for free, but upgrades and advancement cost real money.

In terms of in-app purchases, free-to-play games are the ones people spend the most on. The logic is that by providing a free product, people will get into it and pay a little bit to get ahead or to get past a level that seems impossible (hello, "Candy Crush" level 147!) "The mobile market has really moved almost completely free-to-play," Callahan said. "Paid games are really a very small part of revenue."

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But it turns out everyone loves gambling, even if it's just for the experience. For Android, the highest average spend per buyer was for "Big Fish Casino," a virtual slots game. Big Fish is part of a subcategory of free-to-play games in which you're given a chunk of free credits to start with but have to start paying once you run out of the initial capital.

Remember that nobody can actually win a single dollar on "Big Fish Casino" because online gambling is illegal in the U.S. All the money spent by users is pure profit for the company. The users are buying vapor-worthy credits that serve no real-world purpose beyond furthering more Big Fish "gambling."

The in-app game space uses terms to categorize its users' spending habits borrowed from the language of casinos: whales, dolphins and minnows.

"We find that a game like 'Simpsons Tapped Out' has a fairly even distribution in those three segments in terms of their spending," Callahan said. "Whereas something like 'Game of War,' also a leading game, 80 plus, 90 plus percent of their revenue is coming from a whale—over $25 a month."

Social casinos (like "Big Fish Casino," "Doubledown Casino," and "Slotomania") are one of the fastest growing groups of gaming: revenue is expected to reach $3.5 billion in 2015, according to figures from Eilers Research, a firm that tracks the gaming industry. That's up from $2.8 billion in 2014 and $1.3 billion in 2012.

Churchill Downs, the company that runs the Kentucky Derby, acquired the maker of "Big Fish Casino" in December for $885 million.

Plus, the people who are into mobile casino games are really into them. The difference between mean and median for those games is greater than for other game types, meaning they have more skewed distributions. One iPhone user paid nearly $22,000 playing "Big Fish Casino" in the time period. (Just FYI, the central office for Gamblers Anonymous can be reached at (626) 960-3500.)

Making gaming more mature

The typical "Big Fish Casino" player is a female consumer over 45, Callahan said, highlighting another unique aspect of mobile gaming.

In December, NPD found that 35 percent of its users had made an in-app purchase, more than double from two years prior. So while a good subset of the population pays for freemium, there's still a lot of room for the market to grow. Interestingly, it's older Americans who have the money and are above average in the spending. While having a heavy-spending older population is unique to mobile games, it's not unique to anybody who has walked around a casino lately.

"Typically we'll see [that] on more traditional consoles, spending is driven by younger age groups," Callahan said. "But in this case, we're seeing it in the higher age groups."

Among iPhone users, the 45-54 age range averaged $146 during the period studied, with the 55 and above group close behind, at $145. The older set were big spenders among Android users as well, plunking down an average of $120.

Now, circle up the wagons, crush the candy and run that temple.

CORRECTION: The NPD Checkout Tracking system allows users to opt to have their purchase behavior tracked. The system has some 2 million users distributed around the nation. The system's rewards and size were misstated in an earlier version of this article.