Using the YouTube service while not logged in will save four distinct cookies to your browser. Their names are, YSC, VISITOR_INFO1_LIVE, ST-12wz3df (Most Likely Different For Each Visitor), GPS and dkv. While it of course is impossible to reverse engineer their utility without access to Google's code we can logically assume some of their purposes. "YSC" is most likely, YouTube Search History that tracks and help populates the search bar and it expires when you exit the page. I would assume that either, "Vistor Info" or "ST-12wz3df" would be what is actually acting as a tracking beacon.
Google uses MyActivity to formally keep track of user data, while in the past this, along with YouTube History could be viewed be visitor's not logged in, this is no longer the case.
In my personal experience, I have not had issues with video recommendations when using a private mode in the browser, I also have not had issues when I blocked cookies from youtube.com, google.com and doubleclick. Because of this, I believe that cookies are the reason why your suggestions are being based on your past videos and would recommend clearing you cookies and cache, using a private mode or blocking aforementioned cookies.
One more thing, while it may appear that the suggestions are being paid for, they most likely are not. As per many laws, sponsored content must be labeled as such, Google and YoutTube appear to be following these laws.