It sounds plausible, but I haven't read the series recently enough to have much of an opinion about it. Where do the Weasley twins fit? They're a couple of cost-shufflers in some ways, but maybe this theme explains why they didn't get a big part in the final battle (something I was looking forward to).
You might be able to present Umbridge as a cost-shuffler, but it certainly isn't as obvious as in Voldemort's case. Actually, while she's a great villain, I'm not sure what her motives are. Is it just that she doesn't like Hogwarts and/or Dumbledore and/or Defense against Dark Arts, or is her flaw (in addition to sadism) that she wants to be in charge of things without knowing anything about them?
Anyway, willingness (or not) to pay the cost of what one wants is probably a big theme in the books, even if it doesn't cover everything.
This entry was posted at http://nancylebov.dreamwidth.org/467648.html. Comments are welcome here or there. comments so far on that entry.