Jevons Paradox. Build 2x the thing, whether it's roads or houses, demand only gets worse.
Now I bet that expanding a road not by extra lane, but by ten of them, would exhaust all the "latent demand" and then some. Similarly, if the supply of housing were to increase tenfold, perhaps we'd run out of speculators?
Then again, leverage means they can probably absorb infinite supply - just keep loaning and buying to keep the pyramid scheme going.