For me, it was a pair of merrell shoes on sale. They have lasted 3+ years, have great grip in the snow and ice, and so comfortable, my feet don’t hurt after wearing all day.
Never cheap out on anything that comes between you and the ground; shoes, tires, a bed.
What have been some of your good purchases under $100?
I’ve definitely spent more than $100 total over my lifetime on La Tourangelle garlic oil but it’s about $9 a can and I use it constantly. Gets garlic flavor in stuff without fodmaps.