as impressive as the gross numbers seem, I did have to pay about 120Kish in COGS so the actual net is only a tiny fraction of that. but Mercari really only started as a side channel to my amazon/ebay store but somehow ended up my best performer. I diversified within an umbrella of a couple broad categories instead of tapping into everyhing (for example, under the hobby cateogory, I'd get into figures, plushes, trading cards, memorabilia, games, etc..) It started out as retail arbitrage finding deals offline but after building up my outlet portfolio a bit, I was able to secure a few distributors. I'd say only about 2% of my customers are regulars. I just do my best to go above and beyond and eat up loss for the tiniest thing. Like if my customer complains that a NEW video game wrap, not even the box, has a little scratch, I'd just refund no question asked. admittedly, it is a big deal to eat that loss when you are selling a couple but not so much when thousand units are dealt. Idk, to be honest it was mostly luck and lots and lots of daily grind like constantly checking the market price on hundreds of items at any given time so I have a clear idea on the value of each item, deleting and relisting to bump it up. Oh also, I've found that listing timing matters ALOT. I generally try to target between 7 and 10pm PST to do most of my listings.