I've sold individual photos and issued "full rights" for as little as $700. This was an image that I otherwise would not have a use for. It was also to a large corporation that had deep pockets.
Why does this client want full rights ? Does he understand the differences ?
Perhaps he just wants to do whatever he wants to the image. i.e. make prints, cut outs, banners, TV ads, etc.
If you would have no further ability to be compensated for a photo of this client, I would charge the regular fee for a portrait, and add on whatever you feel is fair for his "right to do whatever he wants" to it.
Is that vague enough ?
