National prestige- you can tell from the commentary nobody ever really believed it would make money
Taxpayers have always had to pick up the tab for expensive white elephants. And from time to time we've looked at various historic examples (eg here). But it's pretty clear today's white elephants are in a different league to the mistakes of the past.
Take the Brabazon airliner. That was the giant eight propellered turbo-prop beast ordered by the commissars at the end of WW2.
In many ways it was the prestige project white elephant to end all white elephants. The size of a jumbo-jet, it was far too big for the nascent Atlantic market, even had they ever managed to get it into service. And there was no real surprise when it was abandoned and £12m sent down the swanee.
And yet by the standards of today's elephants it was a bargain. Because relative to GDP, £12m is only equivalent to about £1.5bn today. Which is chump change.
Today, the commissars think nothing of blowing £2.2bn on a madcap housing scheme, or £20bn on a madcap Olympics.