So once they are making probably around 35k (worst case, depends on standard of living) its probably no longer a moral issue. These things are always fuzzy to me since there can be a dizzying number of factors involved.
However, in this topic, the specific profession being discussed is teachers and I was listing to guy the reasons I believed teachers were underpaid, due to the importance they play in keeping our economy a first world one and with education of children being such a long term investment. There are cases where the market provides a perfect solution and there are cases where it doesn't. My view is in this case it doesn't, because I see education as an infrastructure issue (like health care, roads and bridges, clean air, a court system, etc) moreso than a market one. Infrastructure is far more fundamental because it makes advanced economies possible. We should not allow capitalism to eat itself (or else we all lose), so some things should be public investment.