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?
A cheap beginner ukulele. Less than $100 gets you a new decent/good quality uke. (And $100 goes very far for a used one.) There is a whole world of music, musical styles, clubs, jams, online communities, and free resources. And uke players are generally kind, funny, and generous. “No big egos with tiny instruments.”