Korean mobile publisher Com2uS knows plenty about in-app purchases and micro-transactions thanks to its experience in its home market.

Its first iPhone game to try the business model was online baseball game Homerun Battle 3D.

It features over a hundred pieces of equipment from sports company DeMarini that players can buy to improve their performance or just make their player look better.

We caught up with Joony Koo, Com2uS' team leader for global business development team, to find out how successful this had been.

Pocket Gamer: What have you learnt from implementing in-app purchases in Homerun Battle 3D?

Joony Koo: There are people who are willing to pay for in-app items. However, the game balance for such items is very important and if it's not balanced, downloads will drop.

What proportion of players have been buying them?

About 35 percent of users have bought in-app items.

What we've found is that if people like the game, they're more willing to buy items. Players who either aren't very good and want a headstart, or who are less willing to make an effort, will also buy in-app items.

What price range are you using?

The price range goes from 99c to $19.99.

The price/purchase curve isn't as even as I had thought though. My assumption was the 99c items would sell at least 20 times more than the $19.99 one. But this isn't the case at all.

What ways have you learnt to encourage users?

The game itself is all about competition, so people who are losing most of the time are bound to buy items.

Also, we've been putting up contests where users upload up their best moments as a screenshot. So, being able to show off their customised characters worked.

Have in-app purchases had a significant impact in terms of revenue?

Well, it's helping for sure. I would have expected 30 percent of additional income and it's roughly there. Also, it place the game higher in the Top Grossing chart too so this helps increase downloads.

Will you be implementing in-app purchases in future games?

This depends on the game. Some games will have in-app purchases, but not all of them.

Is there anything Apple could do to encourage more use of in-app purchases?

The current micro billing price range isn't micro enough. There needs to be more breakdown of the price settings. We should be able to sell items at lower prices such as 10 cents.

Thanks to Joony for his time

You can try out Homerun Battle 3D, priced $4.99, €3.99, or £2.99 via this App Store Link.