Maybe but they have to wait a few minutes to post and typing captcha every few minutes shouldn't be that hard. At least that "check the box" captcha. Also, they'd quite quickly move on to the higher rank that would not require captcha, so this one can work quite well.
If the captcha is only shown to delete posts, most Newbies will never even see it. Even the spammers won't be bothered by it, but it can end this paid bumping.
I'll try to scrape a list of involved accounts to be nuked.