My apartment cost 12.000 $ ages ago when I first got it, it's listed as 100.000 $ now, and that listing is determined by the co-op I belong to. We each get votes, but so far the others are more comfortable paying less taxes. Real market value would be over 250.000. That's pretty annoying because it's a serious incentive not to sell when you know you are going to lose half the actual worth.
I wish I owned the thing fair and square, but then of course it wouldn't have been so cheap to begin with.