Some things are considerably less expensive than most supermarkets. Some things more, and the produce is not as fresh. I get good value on frozen fruit, nuts, wine, cheese, and the soup.
If I’m hosting a dinner and don’t want to spend too much time on appetizers or deserts, they have some good choices, at reasonable prices for ready-made.
I’ve seen a lot of stuff from Trader Joe’s brought to parties and potlucks - what I’ve tried has been good.
-JT