How much space does one family need?

I'm pretty sure that the family of Mukesh Ambani will never complain that they "need more space", since their new house has been built in Mumbai.
The house has 27 stories, a height of 173 metres and about 37.000 square metres of floor space. Among others, it contains a car park for 160 vehicles, a cinema with 50 places, a ballroom, at least one swimming pool, several helicopter landing pads, a health club, a dance studio... and many more rooms.

But size isn't everything: it also hosts a staff of 600, that keep everything running smoothly around there. And that's all for a family of five...

In many ways, this entire project is insane and slightly off-putting. But at the other hand: it's not just a showy building but also a load of jobs. And since it's so clearly present in the city of Mumbai (unlike the multi-million dollar mansions of Bill Gates and the likes), it might even draw a bit more attention to architecture and design in this city. Even if you think the project is ludicrous. Even if you think it's shameless to flaunt your wealth so publicly in a city with so many poor people. Even if you think the design by the Chicago-based architects Perkins and Will is unelegant.

Similarly: it might be stupidly oversized, but the prize isn't that shocking: apparently, the house costed about 44 million pounds in construction (about 55 million euros) to build, according to the Guardian. And that's a lot, but at the same time it's not THAT much. What could you buy in your city for that price? Likely not nearly as much, probably partially due to cheap labor in India, of course.
Luckily (for mr. Ambani, at least), the house is worth much more now. Apparently, due to land and property prices in downtown Mumbai, it's worth an estimated 750 million euros (!)