The point that will made over and over again later on that the righteous will get their just reward in the Afterlife is first stated in the Sifre (53) .
The Babylonian Talmud (Berachot 7a) argues that righteous people who suffer do so because their parents weren’t righteous, so they (the righteous children) pay that price — when the children have followed their parents’ examples to one degree or another, that is; and that the wrongful who do well do so because their parents were righteous, so they (the wrongful children) reap that benefit — when they too have followed their parents’ examples to one degree or another. As such its point is that things are not always what they appear to be, and that while some may seem to be righteous or wrongful, they aren’t often or fully so, and that there are other factors to take into account.
Elsewhere the Babylonian Talmud (Shabbat 30b) agrees with the Sifre’s reference to the reward in the Afterlife but adds that one would in fact prefer his punishment in this world to the one he’d otherwise have to suffer in the Afterlife, so one shouldn’t raise the issue of how “unfair” suffering can be.
And finally it indicates (Ta’anit 11a) that point of the matter is that the righteous suffer in the world because of the minor sins they’d have committed (though they’ll be rewarded accordingly in the Afterlife), and the wrongful are rewarded in the world because of the few good things they did (though they’ll be punished accordingly in the Afterlife). This doesn’t seem to explain exceptional “underserved” this-world reward or punishment, but perhaps the case can be made that it would seem to imply that some Afterlife reward or punishment will be exceptional too.
 What’s interesting there is the characterization of the people who point out that the righteous often suffer in this world as people who “fold their arms (over their chest)” in underserved satisfaction, thinking they’ve made a profound and original point, when they’ve not.
(c) 2014 Rabbi Yaakov Feldman
Feel free to contact me at email@example.com
AT LONG LAST! Rabbi Feldman’s translation of Maimonides’ “Eight Chapters” is available here at a discount.
You can still purchase a copy of Rabbi Feldman’s translation of “The Gates of Repentance” here at a discount as well.
Rabbi Yaakov Feldman has also translated and commented upon “The Path of the Just” and “The Duties of the Heart” (Jason Aronson Publishers).