A key issue I have with that $50 price point is that it's never $50. You need a power supply and an SD card, so it's at least $70.

And if you want something better than atrocious storage performance (random I/O performance) you need A1/A2 cards and they are still order of magnitudes slower than SSD/NVME.

So then you buy an NVME hat and select a NVME SSD instead of an SD card and now we are at $90 at least?

And we haven't talked about a case yet. Another $10?

So depending on your needs, it's probably closer to $100 than $50. And at that price point, a second-hand computer - depending on your needs - may be a better, more performant choice. And those 1L pcs can often do idle ~5 watt which is close to the Pi4/5.