The amount of people that were employed to simply test, do documentation, and verify safety alone was staggering, let alone all the smart people it took to develop custom ASICs, FPGAs, mechanical housings, image processing etc. There are physicists who do research, there are sonographers who help achieve the best possible images for clinical scenarios.
The amount of effort it takes to make a high quality, safe, ultrasound is immense. When you add in the fact that you also need to follow a myriad of FDA regulations, even small code changes often require a huge amount of overhead in documentation and review before they get checked in, and then there will be whole teams of people to manage source control.
Ultrasound companies do an immense amount of R&D, but also put out a safe, well-regulated product, and the prices reflect that. I'm surprised the the author in the article found even a low quality ultrasound as cheap as he did.