Photography

I see that Getty sells high resolution royalty-free stock images for $500. I assume that's a license in perpetuity to use the image however and wherever you want but just not be able to resell it yourself. I also assume that means they can keep selling the same license to others for the same photo.

I took some photos that I provided to a major publisher along with an article I wrote that then syndicates my article in the relevant local travel magazine website. They told me they were going to use my article (and paid me for it) and not use the photos I took. I've discovered the company has published one of my photos in four articles (not written by me) in two major City local travel websites, crediting me on the photo but I received no compensation nor was asked permission to uses it.
Normally they get non-exclusive rights to any of my photos they use with my article for an additional $50/photo charge.

I'm trying to figure out a ballpark reasonable fee they should pay per photo. Seems to me at minimum they should pay $50 X 4 articles. = $200? And a lot more if they want exclusive rights to use the image.