Since the concept of predatory publishers has spread over science communities, occurrence of
simple predator-prey reletions in which so-called predatory publishers prey on innocent authors has
become less common. You may see an updated copy of the well-known but discontinued Beall's list
of predatory publishers at "https://beallslist.net".
    The predatory publishers are defined, in summary, by their behavior of dishonestly taking money
from authors offering no effective peer-review nor proofreading nor even stable paper repository. I
can smell, however, subjective and discriminating biases over judgements on individual publishers
and journals in the list. Publishers rooted on Asian or African countries tend to be sorted predatory,
while those from Europe or North America do not. Subjective judgements will fix the north-south
divide, drive emerging southern publishers away toward predatory behaviors for daily survival, and
increase publication/reading costs in favor of northern rich countries. Objective indicators are thus
necessary.
    Below is an example of such indicator. The simplest indicator is pricing in the scholarly publishing
market assessed by journal quality. A similar indicator (price over eigenfactor) was presented at
"http://eigenfactor.org", though data update has stopped since 2010.