Few things incense a western MMO's playerbase quite like the idea of paying for elite items.

Yet with an increasing number of MMOs embracing a free-to-play business model, many developers might be tempted to fall into this trap.

"You can sell them consumables like XP boosts and health potions," noted Cryptic Studio's Jack Emmert, "but don't try to sell players a +5 Vorpal Blade."

The reason for his warning is the 'pay to win' stigma, something that Emmert defines as "the ability of a player to purchase a significant gameplay advantage that is not readily available through in game means."

This stigma is found principally in the west, while it's almost unknown in Asia.

"This model exists in games in China, where there's no pay to win stigma, and they're straight-up selling items, and it works fantastically for them."

So how can you reconcile a successful model in China with the passions of your fanbase?

By imitating the typical Chinese gold farmer.

All that glitters

But this gold farmer isn't the type that you know from traditional MMOs like World of Warcraft or Final Fantasy XI - in a Chinese F2P MMO, gold farmers are players who engage in "grind activities" to earn a set amount of a time currency in a given day.

This time currency is something that can only be acquired in two ways: through grinding, or through trading with other players using "microtransaction points" - or currency bought via in-app purchases.

"In this closed economy, there's a constant exchange between players with a lot of time on their hands and those with lots of lots of money to spend," remarked Emmert before clarifying that at no point is a player exchanging real world money with another for their resources.

By splitting desired items - say, armour and enhancements - between the time currency and the microtransaction currency, Emmert argues that the game's balance will be preserved as grinding players and paying players learn to rely on one another.

The golden rule

Emmert laid out a few ground rules for developers to follow if they want to implement time currency intelligently into their games.

First, the rate of time currency acquisition needs to be carefully controlled.

"You absolutely, positively have to put lock-solid controls on it," warned Emmert. "otherwise, players will spend every waking hour trying to break your system."

Next, it's important that the exchange rate between time currency and currency purchased with microtransaction points is controlled entirely by the players. "Let the players choose the value, and then they'll be an exchange," he concluded.

Finally, the cash shop and the time currency store must offer different goods, which is something Emmert implemented in Star Trek Online.

"If I buy the best ship in the game, it's only potentially the best - I need to fill it with the best gear, and for that I need dilithium [time currency]."

In this model, players will need to spend time currency to buy items - which isn't the same as buying items outright.

And fittingly, this concept is one that is familiar to many MMO players - especially if you remove the word 'currency' from the preceding sentence.

"This is something all MMOs do anyway," Emmer observed, "you need to spend a hell of a lot of time to get the best gear in games."