These unattended stands, called Mujin Hanbai, can be seen in some places around Tokorozawa.
These stands are owned by local farmers or gardeners. They place their produce, along with a donation box, here. The vegetables would be sold for about 100yen per bag. It's a lot cheaper compared to the supermarket.
I sometimes buy my edamame at one of the stands on weekends. I like how they trust you to leave 100yen in the box.