OMG THESE THINGS ARE THE BEST PURCHASE I HAVE MADE IN THE LAST 5 YEARS. 
Bought a 2-pack from Sam’s Club, a year later I bought 2 more. They live in my car, except when I’m moving to a different apartment, lol. 
They fold flat, nest slightly when stacked so they don’t fly everywhere when you go around corners a little too fast. They’re sturdy, hold more weight than i really want to be carrying up 3 flights of stairs (haha) and are a real time-saver when you have 37 bags of groceries but no energy. 
They’re great for keeping the back of your car/SUV organized. They’re great for organizing closets/pantries/garages etc. They’re great for moving - saves on hunting down cardboard boxes!! They’re very easy to open and close once you get the hang of it, although you do have to smack the interior corners to make sure they’re snapped in properly.
Although I regret many, many things in my life, I have literally no regrets about buying these. 
TLDR: These are worth it!!! 