One would really look at the rest of the art market to understand how buyers perceive these things. We might have our own philosophical take on the issue. But there are market forces that are indifferent to us. The entire process of the piece coming into being, and ultimately the path that it took to get into the gallery owner's hands, can be grounds for discernment among collectors.
I was actually intrigued by Bob's picture, and mostly for the fact that it contained a good representation of an unusual natural phenomenon. I might have liked it had that not been the case, but it would have left an open question. Surely, anyone who looks at that pictures wonders what the bright spot is. Of two possible answers -- that it is either natural, or painted in let's say -- I would be left scratching my head as to why it was painted in on aesthetic grounds. If Bob then said "yes, I painted it in, but it represents a natural phenomenon accurately" then I would have been slightly more interested. So it's aesthetic value is a function of some of these things.
Not to suggest that Peter Lik or anyone else is more naturalistic, or that any use of the camera is really naturalistic in the final measure, with its artificial white and black points. But the word "veridical" comes to mind here as the right one. Some pictures /conform/ to the truth more than others. There is a difference between a composite and a full scene capture, no matter how stylized. I think this veridicality counts in the nature photography business, because part of the perceived value of the pictures involves whether the photographer stalked the ends of the earth to find the thing that happened once in a century. Otherwise, you can construct beautiful landscapes that don't exist anywhere in the real world ad infinitum, but they wouldn't sell as nature photography. You'd take that skill to Hollywood.