I'm happy that you're finding personal benefit from Gittip. If it allows or helps you to keep providing great work to the community, that's excellent for everyone.
However, the numbers you quote are not good. $13 is an amount that a Bangladeshi garment worker earns in a week or so. It's nobody's aspirational goal to earn that in a year.
It may be the case (in the wider population) that such disproportionately small rewards actually discourage contributions compared to volunteerism, as it provides a (very bad) point of reference to compare the value of open source work to paid commercial work.