Chipboard was one of those things invented twice simultaneously during WWII, as the Germans and Americans looked around for resources to exploit and noticed the massive amounts of sawdust they had piling up. Chipboard cabinetry and furniture starts to emerge in the 1950's. Ikea was founded in 1943 and started selling furniture in 1948. So cheap particle board furniture existed ~80 years ago, and did indeed sell well.
Yes, but both that and the style linked in the other comment are more complex than the Japanese style sandals. They are just boards with some holes drilled and knotted cord put through the holes. Some have two other pieces of wood underneath them to raise them off the ground a bit (maybe they work better in mud?).
They look like something you could take an afternoon and make enough new ones for your whole family, if you've got some wooden planks and cord.
Clogs look like they'd each take a while to carve and would require more skill to craft.
Though I don't know how common either of those were among the poorest of each region.
My grandparents deliberately saved up for the expensive oak furniture. It was meant to last the rest of their lives (which it did). They had a different mindset than me and you who want something nice looking that doesn't burden the bank account too much
That and I didn't want to buy solid oak furniture when I lived in apartments and had to move on a dime because the landlord wanted to jack up rent or pull something... Again.