yes it is true that flats cost much less outside big cities - but they gained value on the same scale
Well, that same flat in Slupsk was apparently 50,000zl in 2001 and has had at least 10,000zl spent on it since then, so it hasn't even doubled in value.
my mum bought a studio flat in a very small place in Opole region in the year 2000 for 120 000 PLN and we sold in in 2008 for 330 000 PLN
So you got in the region of 10,000zl per sq m? That's pretty much Warsaw prices!