Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.
I wouldn't worry about this list. It seems to be from the BCN Ranking list in Japan. I don't know exactly which shops they survey, but it is less than half and the top selling cameras always seem to be at the cheaper end and often discontinued models. Another thing that works against Pentax in this ranking is that, unlike other rankings, each colour and kit is listed separately. So the K-50's sales are split into four colours (black, white, pink, order colour) and five kits (body, 18-55WR, 18-55+50-200WR, 18-55+55-300, 18-135) meaning a total of 20 kits. If you look at other websites (kakaku.com / yodobashi.com), you'll find the K-3 in a respectable position. It might do better when the price drops below the psychological barrier of 100,000 yen.
But I think it's important to remember that, while Pentax seems to be doing better these days, it is still a minor player in Japan. And I found the same thing as southlander in Kuala Lumpur. Very few Pentax cameras, although I did see a guy with a K-3 and DA20-40mm and I found one shop in a mall with a fair range of Pentax products.