If I accept recruiter interviews, I'm putting myself at a disadvantage if they place an ad. Even if the manager did those exact things or strongly indicated that you were the best candidate, until you get an actual offer, you don't know if those words were sincere. You seem to have concluded that if it weren't for the newspaper ad, you would have been hired. You don't know that. You also conclude that the company hired someone who answered the ad to save the commission the recruiter would have received if his or her candidate was hired.
Recruiters can receive compensation when the candidate is hired, which is a contingency fee.
But not always. Recruiters also can be hired to find someone for a position for a specific period and get paid whether or not they find the right candidate. So you don't know whether the company saved a commission fee. You also make the assumption that recruiters are your only job-hunting tool. They are one tool.