Just three and a half weeks passed since the iPhone 3G became available in Japan and Softbank, the phone’s carrier in this country, already made major changes to the domestic pricing plan.

Although the Japanese data plans were quite reasonable in comparison with other smartphones, Softbank today issued a press release (in English) in which the company announced a quite significant price drop. From this month on, iPhone owners in Japan will be charged a minimum of $27 per month, down from a monthly minimum of $72.

But the lower prices are only applicable to a certain segment of customers. Softbank changed the so-called “packet flat-rate full fixed charge”, adding two ceilings in data usage. The iPhone is now more attrative to the non-hardcore users and Softbank itself says it aims at making the device “available to an even larger public”.

This may be a sign the intitial buzz has worn off already and Japan is a difficult environment for Apple after all.