Oh, it's definitely far more than tens of thousands of users. Those free filesharing sites (particularly those with a "Premium" option available) have been used on the clearnet to share and make money (for both the user and the site owners) of objectionable content for as long as they've been around. The sites are all on the clearnet but the users operate from Tor messageboards for the content. It's not that it's a vast operation, it's a vast <i>market</i> as old as the Internet itself. And that's just the deep end of the iceberg, between Discord, Telegram, messaging apps, etc there is millions. It's nasty and if you fall into groups with degenerate people it doesn't take long to figure out how many people do it.