I think one of the most frustrating problems in starting and operating an online store is the ability to load and keep up with all the products. Especially when there are over 1,000 of them. I have started a few sites only to be overcome by the time consuming efforts of manually entering all those products. Then trying to keep them updated.
I have dabbled in csv files but Shopify is probably one of the hardest to format. That's a good thing for all the SEO abilities it has. But I haven't had success formatting a file for it. And the fees to have someone else do it on a consistent basis can become pretty hefty. Especially when you don't have sales coming in.
I have seen a few companies that say they will intergrate suppliers and keep the inventory updated. But the suppliers are mostly run of the mill and not of a niche variety. How do you do it?