Thanks tomb. I realized it needs a PSU, an SPDIF to I²S converter and maybe even an output buffer. But even the Buffalo and the AckoDAC need these things, so the DAC itself is still 1/6 the price of those.
Though it's not a very good comparison because you can't have the Buffalo as a kit, only as a fully assembled board. I mean, soldering the board up is the best part of the whole DIY hobby, so why not offer a kit?
But yeah, when I look at all the other modules needed, it goes get expensive really fast.
It is my understanding that ESS chips are sold under NDA, so they're not allowed to resell them, they have to sell them as a complete item.
Even if they could sell them as kits, the soldering difficulty required probably means they wouldn't.