It varies, basically what they do is have paid drones who might do some of the trickier spam filter bypassing if they can't automate it, but it's rare they can't automate it, like cracking those image captcha's which only serve, like child proof bottles, to hinder those who actually need to use them.
That's why adding layers of bot tricking turing test type questions is a total waste of time, if they are actually too tricky to crack algorithmically, they'll just pay someone in Belarus or India or Bangladesh to answer the question as they appear, leaving the rest to the software to handle.
Most of it is fully automated, it's software you buy on the spammer underground, comes with free trial versions of course, that's how I learned the basics of how it works, then you go to secret channels and rent someone's botnet for x hours, then run all the stuff you want, the software does most of it.
Email spam is different but uses similar methods to gather it and send it out, but no, it's not efficient to have to pay anyone a per post/email type fee, even if it's just a few pennies per, that's usually all they make per anyway.
All good spam trappers and filters learned ages ago that you filter behaviors and patterns, not hard coded things.
There are people on the other side, but they aren't at all how you imagine them, could be an office full of monitors with people tracking stuff scrolling endlessly in front of them, then reacting now and then when prompted, could be someone testing stuff to make sure it works, just like myog guys do to their stuff, there' not a huge difference in mindset really, which is what most people don't understand about spamming and spammers, it's just a job for most, a way to make easy money off suckers. Could be one kid in his room under his parent's house, tracking a bunch of monitors, having a hard time explaining where he got the money to buy his 72" widescreen tv and rack of computers, often is in fact. Rarely does it get personal, although I must admit once on a client's forums, the spammers were clearly enjoying letting me know when the filters had failed by plastering the forums with extreme russian hardcore p0rn, a touch I found funny, client didn't of course, but it was just the spammer's way of thumbing their noses at me. Best never to take the stuff personally, it really just is a game in the end, not their fault people not only leave their proverbial doors wide open, but then invite them inside as well.
And that's it, won't offtopic further, heh, most people roll their eyes and groan at this stuff, so better to talk about fun stuff like sewing a new backpack.