It seems that Sony is set on further monetizing the PlayStation Network in some way. Sony Computer Entertainment chief technology officer Masayuki Chatani discussed a variety of possibilities in a recent interview with Nikkei (via Computer and Video Games), including monthly fees and per-item charges.

"Servers and the like have running costs... after we sell the hardware, though, we continue to sell products such as content and services," Chatani said, noting that Sony will "face difficulties" if they depend on a "sell-and-forget model."

"We expect to see considerable growth in digital content, such as game download services, avatar items and the like. We can also accept payment in a growing number of ways," he added.

"In addition to single-payment packaged software, there are also schemes like monthly fees or per-item charges. I think this variety of payment methods will bring about a diverse range of playing methods, too."

Sony seems determined to find some way to get more money out of the PlayStation Network, possibly to make up for the losses they are reportedly suffering with each PS3 sold. Sony CEO Kaz Hirai earlier said that they are "studying the possibility of introducing a subscription model, offering premium content and services, in addition to the current free services."

For the moment, monthly fees remain purely hypothetical. Look for additional hints on where Sony plans to take PSN when GDC and E3 roll around next year.