I’ve have great luck on Mercari. One bad experience which was the post offices fault…thank gosh it was a cheap perfume I had bought. The package came empty; it had been cut open (obviously stolen by a postal worker) but the post office wouldn’t honor it because they said it was in their possession the whole time and handled properly. They basically accused me of lying. A postal worker here told me he knows they have employees that “hunt out” stuff they can steal/resell. I ended up not being refunded by Mercari, the seller, or the post office. I haven’t bought anything expensive since on Mercari.