Well, if housing construction cannot keep up it would balance out the quality of life, right? People will move as long as negative QOL delta from expensive housing is, in their view, less than positive QOL delta from other sources.

As for the homelessness example, that is my point exactly, and the general problem with welfare state. You have to choose - restrict the access to welfare state specifically, restrict movement generally, or don't have a welfare state. I do not view welfare state as a sustainable QOL improvement (or a QOL improvement at all), so I am in favor of the last option. For me, people moving in to abuse a local welfare option is a positive development. Contrary to GGP(?), the localities that get punished are not punished for "improving quality of life"... they are punished for stupid policies.