EIGHTEEN months ago, online used-car retailer Carvana had such great prospects that it was worth US$80 billion. Now, it is valued at less than US$1.5 billion, a 98 per cent plunge, and is struggling to survive.

Many other tech companies are also seeing their fortunes reverse and their dreams dim. They are shedding employees, cutting back, watching their financial valuations shrivel — even as the larger economy chugs along with a low unemployment rate and a 3.2 per cent annualised growth rate in the third quarter.

Here is one largely unacknowledged explanation: An unprecedented era of rock-bottom interest rates has abruptly ended. Money is no longer virtually free.