Here I don't quite agree that we have the assumed 25k persons holding XMR. I would estimate it to be at the most half, most likely around 7-8k holders, but I'm really just ball-parking as we don't have any good way to determine how many are out there.
Obviously we are totally guessing, but Poloniex has 71k accounts registered (from the bottom of their home page). Given the prominence of XMR on that exchange over the past year I would guess a pretty significant portion (obviously the preceeding three words describe a very wide range) of that number either has XMR or has traded it (but may not happen to own any right now).