My point isn't that housing costs as % of income can go arbitrarily high without any negative impacts, it's that the study/headline is misleading the reader using a definition of "unaffordable" that is inconsistent with their expectations. "Unaffordable" makes me think that the teachers are struggling to meet rent and have to cut non-discretionary spending to make ends meet, whereas the reality (ie. the 30% mark used by the study) is closer to "have less discretionary spending than wanted".