For $10 this seriously makes technology look like magic.
How can you even make something like that for practically nothing?
It's not really a calculator, it's a repurposed ultra low end Android tablet. And $10 in no way reflects the cost of the components - somebody just bought a load of these unsellable old tablet boards with screens attached and turned them into something with slightly more value.
Cool, because you generally associate this sort of crap with mountains of e-waste. Bad, because Chinese factories are constantly churning out junk like this, and most of it never gets a second life.
But you can buy a way more powerful, more modern version of the exact same thing, still in tablet form, from Ali Express for around $30, that would be a lot more useful if for some bizarre reason you wanted to turn it into a weak emulation device. Also, it's not "running" Doom Eternal, it's streaming it from Steam like anything with a screen can do.