On May 18, 2005 then Bandai had published the sales figures for .hack//IMOQ (Infection Mutation Outbreak Quarantine) combined. Here is what they had to say:
This is an excerpt from the attached PDF file, but the English of it says as follows:
So from it's first volume to it's forth volume over the course of 20 months they sold 780,000 units in Japan and 1.73 million (1,730,000) units world wide
21664.pdf