I just got a R36s retro handheld console for 31€ (US$35) including a 64GB microSD and shipping from Aliexpress. Apparently sometimes you can get it for as low as $25. It has a IPS instead of a eINK screen, but the CPU, RAM, Storage, battery etc. are as good or better as any ereader, so it is possible to get a tech device for way less than $80-100. But I guess it won't count as mainstream and nobody should expect support. It relies on open-source software (ArkOS) and ships pirated roms of abandoned game consoles, so there is no option for the manufacturer (unknown) to earn more after the sale.