Let me start by saying that I have NO affiliation with Amazon or the retailers selling these Pilot Iroshizuku inks
On Amazon UK, if you search "iroshizuku", you can find almost the whole range for around only £15! Normally, one would have to pay around £30 for these. They're even shipped for free! I'm not sure if these retailers ship to other countries for free or sell elsewhere for the same price.
So, if you want an Iroshizuku ink, but haven't gotten one because of the price, you're in luck!
Unfortunately, the prices do change from time to time, but you can track the prices using http://uk.camelcamelcamel.com/
Some links to the more popular inks:
Unfortunately, Tsuki-Yo was available, but I can't find it at this time. It will probably be re-stocked soon with the £15 price tag.
I hope this was useful to you.
Edited by a.zy.lee, 11 May 2014 - 12:57.