Suppose I have a house I bought for $1000 (2015 USD), but the realtor tells me I can now sell it for $2000 (2015 USD). When I sell, that $1000 eventually comes

Suppose I have a house I bought for $1000 (2015 USD), but the realtor tells me I can now sell it for $2000 (2015 USD). When I sell, that $1000 eventually comes from someone else's productive labour, which will be transferred to me. As the buyer, I can pay the $2000 by borrowing from someone else and servicing that debt from my income. The $1000 capitals gains that got pocketed are of course the buyer's future income. So we can have ponzi asset bubbles in housing all we like, but right at the heart of it, the drivers are how much actual working people are willing and able to borrow, and how much they can pay to service their debts. Put another way, their statement is that when everyone is maximally indebted and has no disposable income, the music has to stop.