This one is a chronicle bound to become obsolete, although prices in Japan are remarkably stable over the last years. But nonetheless I wanted to offer some information on the costs of inks nowadays.
Ink prices are highly dependent on the market, thus defying globalization trends to homogenize them. A clear case in point are the Pilot Iroshizuku inks—their price in Europe is almost twice that in Japan. Reasons for that? Please, ask Pilot directly.
So, here I am publishing a list of ink prices in the Japanese market. I show only the catalog (MSRP) price. Needless to say, this list is far from complete—there are some other brands for sale in Japan, and there are other presentations of these inks. Among the first, I can think of the Hakase Real Sepia ink at JPY 6300 per 50 ml. Of the second, the recent release of a three-20-milliliter inkwells by Pilot.
Prices in Japenese Yen (JPY) for inkwells. VAT in Japan is 5%. Please, click on the table to enlarge it:
Now it is up to the reader to decide what to do with this information.