If you want to try and estimate it, take a look at how frequently a company like ABU runs out of stock. They are ordering diapers by a minimum of a shipping container (most likely a large one). In my own experience they run out of size medium SDKs every 6-8 months or so, and they have multiple brands. Not sure how many SDKs fit in a shipping container, maybe 8000. If they sell 10 containers of diapers a year that would be 80,000 diapers. They'd probably want to sell for at least $1 more per diaper compared to what they buy them from in China. So after shipping ($3000-$4000/container), staff ($15/hr/person), warehouse costs ($1500/mo) they aren't getting rich, but they are enriching the community greatly. We should probably drop these businesses a thank you card once in awhile.
ABClothing in order to make a fair amount of money you'd have to be willing to go to China or one of the other 'cheap clothing' countries and enlist a company to make your designs and could offer a selection as large and beautiful as what Privatina does. I think the Chinese govt might be subsidizing shipping directly from China now, because a lot of sellers on Amazon and Aliexpress are offering free shipping where the product is shipped directly from China (eliminating warehouse and container fees for the seller).