It's the humans, stupid, and boy, are they stupid
I think the single approach that would most hurt the criminals would be if the suckers would stop installing their apps, and the single kind of information that would most deter the suckers from installing the apps is knowing the REAL financial motivations of whoever is distributing the app.
Of course, that kind of "reality" is too much to hope for, but if some attempt were made to present the financial information, then it would help in a lot of cases. Most of the legitimate financial models are pretty well known, and the google could basically offer them as selectable options--and in most of those cases the google could offer some independent evidence as to whether or not the developer is telling the truth, and lock that part down so the developer can't tamper with it. Does the developer say he will get money from ads? Then the google can say they are paying advertising revenue. Is it a limited version for a paid version? Then the google can report that a paid version actually exists and is actually earning some sales.
Of course the google doesn't understand this, do they?