Many photographers sell their photos as stock photos to sites where you can pay to have accounts. Like, I could sell my U2 photos to Getty Images for a certain amount and beyon that, Getty is free to offer them for sale to other media publications. Usually, the more you pay, the larger photos you get and more access to reprinting them. For example, a news publication can have a paid account with Getty Images and then they have paid for the right to download these images and print them in their publication. I'm guessing many of these eBay sellers do the same thing, since they always seem to have tons of pics of a wide range of celebs. The problem is that I doubt they've been given the right to reprint and sell the images as photos (instead of using them in a publication), especially without printing any copyright or credit on the photo.
You can get these copies by signing up for an account at a photo site, or usually just browsing the net. Many people who have accounts will post photos on their sites or save them in their own galleries that become open to pretty much anyone. For example, a few PLEBANS used to have a paid account with a photo site so we could post unwatermarked images here and share them.
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