How do they work?

Hello. I'm just curious how do those link building/outreach companies work. I mean, not some shitty PBN companies but REAL agencies. Let's say some agency offers 50 DR+ link for $400 with content included. And what I mean is they outreach to bloggers, do they pay them to put a guest post on their site? Or they get it for free? Like high quality guest post is a good value for bloggers tho. So how does business model look like?

Like client pays agency e.g. $400 for DR50+ guest post. They hire writers to write high quality post for lets say 40$. So they have $360 in profit or also pay bloggers for a guest post?

I just dont get it and would love to explain someone it for me.

Hacked links

Honestly I'm seeing more and more of this...

No way serious companies do this shit.

You can't say exactly for sure but obviously theres some type of exchange. They could be paying a resell cost or exchanging guest posts. Who knows? Anything is possible, just start doing guest post outreach and you'll see.