The same for so many other things. Get your car fixed because one tiny little piece broke. On the bill you see that the part cost was $3.00. The labor was $120 for 20 minutes of work. It's always the labor.
(I can't remember if I've told this here) Over the years my father was given several really nice paintings or prints from companies he was dong business for. My mother, wanting the frames to be just as nice, would take the paintings to a guy they knew who built frames as a hobby out of quality wood adding decoration of his own as well. He charged I think between $60 and $100 which included the cost of the wood. After they moved, they got another painting, and Mom told me that the place she took it to quoted a price of around $1,200 to do a frame/matting job similar to what the guy had been doing for her all of these years.
It's always the labor.