You make it sound like an ultrasound setup is a bulk consumer device. They very much aren't. They're quite low turnover items, and require significant specialist knowledge across a couple of fields to make. They're not consumables - if you sell one, it could be in service for 5, 10, 20 years. $50k for this kind of lasting professional tool isn't that much. I'd say $50 might be a touch high for this kind of thing, but not by much, and depending on the model, not at all.
I used to work at a place that made medical electronics, and the idea that 'because smartphones that are churned out by the million only cost half a grand, every other electronic item should be similarly cheap' is just wearying.
If there would truly be an enormous price pressure on hospitals and clinics driven by a free market setup, I am pretty sure they would turn around and talk to said equipment manufacturer: Hey, we know you are selling us a desktop with an audio card. We are pretty sure you can still survive if you reduce your $50k profit and sell us the same equipment for 20k or 10k. Then, said equipment manufacturer, would have to increase volume by starting to sell it to developing markets (what a novel idea) or find ways to produce it cheaper etc etc... but I get it - these are daily considerations of entire industries that the medical sector does not need to be concerned about. What if we tried and see where this would lead though? Right now, I think, we have a pretty good idea how a healthcare system looks like when it is run without any price incentive or cost assessment.
The high price of an ultrasound setup has nothing to do with the desktop PC component. Ultrasound probes are the specialty part of the hardware costings, the clinical know-how for the software is another expense, compliance is another, and low turnover contributes yet another.
Similarly, 'just sell in developing countries' is an utter throwaway line for medical devices the way you're using it - and you'll find that these products already do sell in such markets anyway (what a novel idea indeed!). Not to mention that developing countries have extremely limited medical budgets, and 'allied health' stuff like ultrasounds are luxuries - they're available and have sales teams, but the turnover is extremely low.
I used to work at a place that made medical electronics, and the idea that 'because smartphones that are churned out by the million only cost half a grand, every other electronic item should be similarly cheap' is just wearying.