Who doesn’t love a good freebie? Certainly no one I know. It doesn’t matter if it’s a keychain or a speedboat, the allure of that-which-we-do-not-have-to-pay-for is pretty damn hard to resist – whether we need the thing being given away or not! Nowhere is this more apparent than in the emerging world of mobile gaming, where freemium apps (apps that are free to use, but include in-app purchases) are all the rage. At this very moment, billions of idle thumbs around the world are engaged in epic battles between plants and zombies, building up armies to defend entire towns, and matching up colored candies in order to “crush” them.

Freemium’s rise in popularity is hardly surprising

In-app purchases can be dirt cheap, and they offer instant gratification. Currently, only 4% of users take the digital bait. That might seem like a drop in the ocean, but when you consider that Candy Crush Saga alone has 93 million users playing more than 1 billion times a day, that works out to some serious spendage.

Enough to finance the development of the game and then some!Wondering how the freemium model works? Allow me to break it down for you. You come up with a wickedly addictive game (think Angry Birds meets Flappy Bird, with a Candy Crush coating) and distribute it for free. Once players are suitably hooked, you reel them in with paid-for extras: an unlocked character here, a bonus life there.

Perhaps an option to customize the look and feel of the game – the possibilities are limitless. And because these micro-transactions are integral to the gaming experience, users don’t seem to mind the additional expense.

Game developers are not the only ones jumping on the freemium bandwagon. Spotify recently opened the gates to its much-loved music streaming service, under the banner “Music for everyone.” The company’s new freemium philosophy should sit well with those who believe that music is as much a basic human right as clean air, water, and… free Wi-Fi! Spotify’s mobile offering does come with a caveat, however: it shuffles your playlists, only lets you skip up to six tracks per hour, and won’t let you listen offline.

Oh, and playback is subject to the occasional ad. It’s a trade-off most are willing to make in return for free ear candy, but one that Spotify hopes will gently nudge users into upgrading to a $9.99-a-month premium subscription that removes all of these restrictions.

Also dangling a golden carrot in front of its users is the ubiquitous note-taking app, Evernote. As with the aforementioned apps, Evernote shows just enough leg to tantalize, while holding back premium features for paying customers. For a mere $5 a month, users can enjoy offline notebooks, collaborative note-taking, increased storage, and more. Its creators are banking on the fact that once users are tied up in their ecosystem, they’ll be eager to have all the extra bells and whistles, even at a price.

While there’s certainly no shortage of monetization models out there, freemium is perhaps the most user-friendly proposition. It offers the same rush you get when you discover a hidden Easter egg in your favorite video game that lets you run faster, jump higher, and live longer. Only this time, the Easter egg has a price tag on it.