The largest cost for any criminal enterprise is money laundering. It costs far more than 50% of gross profits to launder money. With banking controls (yes, they do exist) and stricter laws, it can cost in excess of 80% of gross profits to clean your cash.
Real estate in London might fall by 50% or even by 75%. But that is still much, much better than paying 80-90% to an HSBC banker for a complex, multi-country laundering scheme. This goes a long way to explaining London and Singapore property prices.
Frankly, I never understood why anyone would want prices to go up. If I were looking to move up or down the ladder, I would prefer prices to drop. We don't buy and sell houses based on yields. We buy and sell based on real numbers. If I own a £100k flat and want to move to flat twice as big, I would like both to lose 50% of their value. Then I would get my new flat for only £150k instead of £200.