Most photos are worthless except to the person who took them. If someone uses your photo without permission you have not lost the photo so it does not need replacing.
What he may have lost is the price he could have commanded for exclusive use of the image
By that logic, if he allowed all his images to be used for free, he has not lost anything but the "exclusive use fee".
You are missing two key points:
1) He is losing the expected income from the potential sale. If he says "yes you can use it for free", he will always gain $0. If he says "no you can't use it for free", he will gain $X * P[magazine will pay $X], which is almost certainly higher than $0.
2) If he allowed his pictures to be used for free, he'd drive down the average market value for such pictures. This would hurt him and other photographers in the long run.
I wasn't arguing against not using things for free (aside from agreeing with the parent post regarding small "sample" versions was a way to get the image noticed with lower risk of the full quality version being taken), I was questioning his way of calculating what he has lost through someone using the image without any sort of license.
Nothing is lost as such: the outfit using the image for nothing probably wasn't a potential sale anyway. This is copyright infringement, not theft. While setting his price any way he likes is his right, and he can sue that amount if someone uses the image without permission if he wants, this and "why you can't use the image for free or for credit" are separate issues which should not be conflated in this way. There is a big difference between someone asking for permission to use the image under different times (a lower, perhaps zero, price) and someone using the image without license - they are completely separate issues. One requires negotiation or just a straight no, and it then goes away. In the other case there may be need for legal redress.
What he may have lost is the price he could have commanded for exclusive use of the image
By that logic, if he allowed all his images to be used for free, he has not lost anything but the "exclusive use fee".
You are missing two key points:
1) He is losing the expected income from the potential sale. If he says "yes you can use it for free", he will always gain $0. If he says "no you can't use it for free", he will gain $X * P[magazine will pay $X], which is almost certainly higher than $0.
2) If he allowed his pictures to be used for free, he'd drive down the average market value for such pictures. This would hurt him and other photographers in the long run.