With these ultrasounds, there is such a heavy regulatory framework at work -- from regulations impacting the device itself to regulations preventing hospitals from being built to regulations preventing hospitals from having as many of these as they want -- that they make the actual quantity demanded of these things artificially small. Your point about evolution of the technology also falls trap to this same fallacy: Again, if all of a sudden you are artificially making something much more expensive to produce, it should be no surprise to you that the refresh rate on the device would be smaller. Here you also have the added effect that since we rarely pay for our own medical care and instead rely on insurance, many of the incentives that would exist for companies to make cheaper, faster, better equipment also disappear. Lastly, I fully concede that it is quite possible that there is some basic, inherent quality of ultrasounds that make them more complicated than cars or any other pieces of tech. But that isn't important. The importance is realizing that the derivative of the state of these machines looks very different from other technology industries where competition and the free market are much more of a factor.