edit: I have not read the paper, which Amir points out covers some of my complaints. I am referring to the charts in the video, and have not read the paper, so I jumped to some conclusions. I leave my comments here so people who don't read the paper will be aware of what is not covered in the charts, and that you need this information to come to any conclusions about the market as a whole. Especially the conclusion about no price correlation, and country of origin, it's hard to say how meaningful it is. Certainly China has a lead in performant dacs, but does it really have 115 to 1 advantage over Japan? :end edit
You need to tell the reader how many dacs you tested from each country. And, how many dacs are on the market, at least do a rough survey, so people will know if your selection of products is representative of the general market. Only then does your chart showing the countries the best performing dacs come from make any sense.
Also if the products are new, or now. You have released reviews on products that are already replaced by the manufacturer, which doesn't truly represent today's market. Indeed, this list of dacs includes some from over over 6 years ago. Including these in your analysis confuses whether your data represnts today's market, or the market over a period of ten years. Or more, depending on how many vintage dacs you've tested. We don't know because you don't say.
So far as the price performance comparison, I expect if it was not linear but logarithmic, or the dacs were compared at prices from 100 to 1000 only, then you might see that relationship. At the highest sinad, there seem to be less dacs at the bottom of the price axis than there are at slightly lower sinad. So maybe the conclusion is that you get a little performance at the margins up to a few hundred dollars. At least, that would explain no apparent $100 - $300 dacs at the high end of the sinad chart. Surely that indicates something if you don't skew data by including super high prices well over $1000..