OP checking back in here. I think I've gotten the answer to my question, and find myself in the minority as to considering a photographer's work his/her source of income, and my copying that work, rather than paying him/her, is unethical.
I'm sorry that I didn't make the situation even clearer, in that the man I encountered was holding a new (apparently) studio produced graduation/yearbook photo, and wanted to make an enlargement of the smaller photo he was holding.
The argument was made that if a photo is really old, and/or the photographer is unknown, dead, or cannot be contacted, it's OK to make the copy. I can see the rationale behind this, and the posters who offered this scenario made it plain that they WOULD pay the photographer if they could. I think my conscience could accept this, and I might join them in making the copy.
But the rest of the arguments involved disliking the photographer, disliking the situation (being forced to use an expensive photographer by the school,) or disliking the prices charged. The latter APPEARED to be the case in my encounter (but I didn't question the man as to the specifics in HIS case) and the clerk viewed it that way.
I didn't want to pay the ridiculous fees charged by DD's HS photographer for what I considered so-so photos, so I didn't order any. DH took a photo that year which is far superior, so that is what we have framed and hanging on the wall. Her college photos were very nice (I only saw the candids, not the "official" one) so we ordered copies and enlargements. It never occured to me to go and copy them myself, as I view that almost as "stealing" from the photographer...selling his photos is how he makes his living. Owning lots of "originals" doesn't do him a bit of good unless people purchase copies.
So I appear to be in the minority in my thinking, and I suspect that professional non-journalistic photographers may go the way of portrait painters. (Which I, and many of my friends, have used) They will have to increase their fees to cover lost revenues (ala Sears) in order to survive, but even then, only a minority of people will feel that the finished product is worth the price, so they will decrease in number.