The first thing I learned to draw was a house. It was like the house from the opening titles of Play School – the one I assumed the programme happened inside, even though the square, round and arched windows through which viewers were invited to observe manufacturing processes didn't seem to correspond to the ones on the outside, and it was difficult to imagine how the parts of the show that took place on polished studio floor, backed by seemingly infinite whiteness, would have fitted into that idealised average home. Maybe there was a massive conservatory at the back.

You know the sort of drawing I mean: "A house, with a door, windows 1, 2, 3, 4" – perfectly symmetrical apart from an off-centre chimney on the pitched roof. As I developed as an artist, I would sometimes add a balancing chimney on the other side, with smoke coming out of both. Later, I'd join up the smoke so it looked like it was coming out of one chimney and going into the other, as if the residents of one wing were trying to poison those in the other. That wasn't what I thought at the time – I was not a child who daydreamed of gassings. I just didn't like loose ends.

I don't think I was unusual in my early subject matter, particularly for a British child. What a house is, and that you live in one, are concepts that most of us latch on to in very early childhood and it's not long before we realise that the bigger the house, the better – that some families live in bigger houses than ours and some smaller. This all strikes us before we even learn about money – it plays to our primeval urge for territory. I've often felt that the expression: "An Englishman's home is his castle" should really be: "An Englishman wishes his home were a castle."

I was glad I didn't live in a flat. I remember someone explaining to me that, in big cities, some people resided in such places. Care was taken not to put any negative spin on this but, for me, snobbery was instinctive. Flats sounded so obviously worse than proper houses with proper gardens. "Why would anyone want to live in a flat when they could have a house?" I would ask. I think if I'd been given an answer I'd found satisfactory, I might have remembered it.

Last week, a flat in Knightsbridge sold for £140m. Whoever paid that must despair of ever being able to afford a house. All that money and you've still got nowhere to play Swingball. The reporting of the sale made nothing of this. Confusingly, it focused on how luxurious the apartment is – with a panic room, SAS-trained security, 24-hour room service from Heston Blumenthal's new restaurant and "floor-to-ceiling windows, its own car park and access to a host of spas and squash courts" – as if those things make it worth the cash. I mean, "access" to squash courts? For that money, you could build a new headquarters for British squash.

Posh though this place undoubtedly is, £140m is a ridiculous sum to pay for any flat. Not in the way that it's ridiculous to pay £4 for a cup of coffee – in a vastly greater way. When you leaf through those magazines with adverts for manor houses, with tennis courts, swimming pools, lakes, hundreds of acres of land and rows of cottages, they cost millions – maybe £10-12 million? That means you could buy a dozen of them for the price of this flat. You could probably snap up a whole Greek archipelago for this sort of money.

"Location, location, location," you might say. "Three-bedroom houses cost less in Sunderland than they do in Hampstead." I don't think that's sufficient explanation. The £140m doesn't begin to be justified by the flat's proximity to Harrods and the tube.

But that's the whole idea. It's old-fashioned conspicuous consumption, which is why I don't suppose the buyer will guard their anonymity for long – certainly not from friends. The Notting Hill set may have swapped their ministerial cars for Oyster cards but, on the other side of the park, a different breed of oligarch is still vulgar enough to want people to know they throw out their leftover caviar in ivory containers.

Citing the flat's luxuries makes the sale slightly less of a remarkable news item because they make the purchase marginally better value, although only in the same way that what the government paid for RBS might have been made better value by a complimentary pen. The only reason to have bought this flat is to demonstrate that you're so rich that value is a concept beneath your contempt. So an even flashier demonstration would be to pay more than £140m for somewhere worse – say my flat in Kilburn.

Anyone who could afford to pay a seventh of a billion for my ex-council property with its mouldy bathroom, bedroom doorhandle that comes off in your hand and crackly phone line which, for some reason lost in the mists of 1980s Irish wiring, cuts out whenever anyone walks into the living room, is a plutocrat indeed. I think it would be the ultimate status symbol. The kitchen's nearly new. And with all that money, I could buy Surrey, where I'd have more room for all the piles of old newspapers and empty wine bottles.

Or maybe today's wad-waving billionaire prefers somewhere with more character, a bit of age to it. Archaeologists have recently discovered the remains of Britain's oldest, and crappest, house: a 10,500-year-old hut near Scarborough. It lacks the Knightsbridge apartment's mod cons – in fact it resembles a giant fossilised turd – but, in heritage terms, it makes the Tower of London look like Poundbury.

On the face of it, this brave little dwelling of wood and reeds is a complete contrast to a gleaming penthouse overlooking Hyde Park, but they're both among the fussiest residences of their eras. A handful of cavemen who became too snooty for caves started a fetishisation of shelter which has led to elaborate yurts, impregnable castles, shimmering palaces, dodgy loft conversions, stone cladding and Foxtons. We didn't get where we are today just because we like to get out of the rain. We were driven on by pride and envy. Unfortunately for the state of my guttering, I'm more of a sloth and avarice man.