Bad economics, says Megan McArdle. Excerpt:
The low opportunity cost attached to magic spills over into the
thoroughly unbelievable wizard economy. Why are the Weasleys poor? Why
would any wizard be? Anything they need, except scarce magical objects,
can be obtained by ordering a house elf to do it, or casting a spell,
or, in a pinch, making objects like dinner, or a house, assemble
themselves. Yet the Weasleys are poor not just by wizard standards, but
by ours: they lack things like new clothes and textbooks that should be
easily obtainable with a few magic words. Why?
Addendum: Here is the nerdiest sentence Ezra Klein will ever write.