What do you even mean by "dark web"? Stuff like this definitely doesn't exist on the onionland.
A good blog post would be a detailed tour of this site and going through the process of buying a slave and then interviewing them about their experience, afterward I guess you could let the slave go off and do whatever they wish or perhaps resell them to get your money back since you are unable to take care of them anyway.
I'm fascinated because I track things like this for a living, but have never heard of anything similar to what was described here.
To clarify, do you work on behalf of human traffickers to track and stop leaks about their marketplaces, or is it more to keep tabs on competitors?
Not sites?
One thing I know about the internet, is that there isn't just one of anything, even if it's illegal.
Modern slavery certainly happens - but I've never seen it on silkroad-style websites.
A post by someone online, who once talked to someone who said you could buy slaves online ain't exactly first-hand evidence - Perhaps someone was mistaken, or taken in by darknet scam artists.
This should be easy to prove. Closest I can think of is some Telegram groups you might find in places like Syria, but that hardly warrants the Amazon comparison.