I wouldn't call it the same pattern at all. There's no difference in comparative advantage between one monetary donation and another, and charities targeting causes such as malaria and poverty don't suffer diminishing returns on donations within the range they're likely to receive. On the other hand the differences in comparative advantage between one researcher and another within a particular field can be quite large, and a research subject can quite plausibly suffer diminishing returns on new researchers of similar abilities (see this quote already linked to in this topic.)