I just need to know how to market these better. I also appreciate the fact that you took a little bit of time and effort to explain your business. I've had no experience in large print photography, but you certainly seem to be offering a very viable product which does have intrinsic value beyond the cost of the poster. They may not be benefits in his eyes. He might never be attracted to your kind of product offering.
Reduced cost is a benefit, no question.
And you have already identified that. One neat and powerful way to do that would be with testimonials of the variety of ways that people have utilized it. Or another example, when my wife and I were married, we had a photographer, got the 'proofs' , but did not have the money for a large format picture. If you could convey your solution to me, I would be a perfect prospect. My wife doesn't look too different from the day I married her in 1984, but I look WAY different.