I don't see the relevancy of Mr. Burrows' statement (correct, of course) that "Very wealthy people give less, as a percentage of their wealth and income, than people of much more limited means. For wealthy philanthropists, the value from giving may be in status from the publicity of large gifts."

This is certainly of concern if our goal is to maximize the virtue of rich people. If it is to maximize general welfare, it is of no concern at all. The recipients of charity don't need a percentage's worth of food, but a certain absolute amount.