ISTR that the R10 ceased production around 2004.
The following should be treated as unconfirmed rumor:
One of the things that I heard, but don't know for certain, is that the engineer responsible for the R10 retired, and that there was simply nobody to replace him. With the expertise gone, so was the R10. Another story is that Sony was losing money on every R10 sold, but simply kept them in production as a statement product. The Qualia was developed to replace the R10 as the statement, and also turn a profit while doing so. While the Qualia 010 was an excellent headphone, it was also both finicky and fragile, and the line soon went under. After the Qualia line tanked, Sony stopped marketing statement headphones.