Even low end devices are shipping with SSDs now. The last time Windows 10 was slow for me it was either because it was still on a 5400RPM drive (brand new $900AUD PC from a retailer...) or because Intel had tricked a whole lot of ODMs into thinking the Z series Atoms were desktop processors rather than for mid-range smartphones.
In fairness, the low-end $200 laptops have emmc storage, which isn't what consumers think of as SSD. Yes it is solid state and faster than a hard drive. But it's not typical SSD performance like you get on the $400+ laptops.
eMMC 5.1 (introduced in Jan 2015) has read speeds up to 250 MB/s and write speeds up to 125 MB/s. They're much faster than the earlier eMMC chips, as well as laptop hard drives. Sadly, the early slow chips kind of gave them a bad reputation. They're perfectly workable now for a low-end machine.