I don't know how you get those numbers
I agree that anime business these days is not very profitable in business perspective. But, If we compare Tsuritama sales to the sales of some recent noitaminA shows, It did a good job. Personally I think Tsuritama is great. the ratings definitely are not great but not poor either
And I think you can't just omit the niche factor from Tsuritama sales. Think! If a certain anime is watched by more people or catch more people attention, at least that show will get better potential that more people will buy the BD/DVD. Even If an anime is really good, but only a small portion of people interested in it, that anime will certainly fail in term of the sales level.
Let's see if Psycho-Pass can take the glory of noitaminA back