I agree. You can't compare an Eink Reader with an MP3 player or a mobile phone, it's rather something like a
dictaphone. The market seems to be really small. In 2012, there was a need for cheap handheld deveices and Eink Readers filled that gap. But this gap isn't there anymore, people buy a mobile phone or an Android handheld now if they need a new cheap toy.
Sony would need to raise the prices for their deveices, but this is not possible at the moment since other manufacturers with gated shopping environment charge only 40 or 50 Euros for their entry-level deveices (Kobo Mini KBUP, Amazon Kindle AZW3) and Sony would sell even less then.
Amazon is actually making financial losses with their system, but they want to dominate the market of digital distribution, that's the reason why they are doing this. Sony on the other hand is obviously not that much interested in digital distribution at the moment (at least with digital publications), they just focused on building good and longlasting hardware and cooperations with public libraries and universities. Maybe this strategy was a bit too much oldschool, at least for the US-american market.