Your argument is wrong because one luxury apartment will take up the space of 2 cheap ones, not 20. Also, the cost of making a luxury apartment vs a cheap one,

Your argument is wrong because one luxury apartment will take up the space of 2 cheap ones, not 20. Also, the cost of making a luxury apartment vs a cheap one, fittings, etc. is trivial compared to the sale value in today's market in Paris. The choice isn't 1 v 20, it's 1 v 2. You can't make 20 cheap apartments in the space of one expensive one. Hence why I used 2 instead of 20.