They are pointing out that what the previous commenter said was ridiculous, by saying the same thing with merely other variables swapped in which more obviously illustrates how ridiculous the original statement was.
Yes, it's called a "false analogy", a typical informal fallacy.
There is nothing ridiculous about the fact that people-that-use-more-than-average (over-users: p>.5) are compensated by people-that-use-less-than-average (under-users: p<.5) to establish an average... it's called spread.
Is it at a certain age, or is that only for children born latest at $YOUR_BIRTHYEAR?