I don't think so. Maybe a sepia is just a sepia , but any sepia is not even near to a properly toned image and there are people out there there who mastered that part of photography working for hours even days on their images trying every possible solution for the final work.
And I'm sure that if they give the originals to designers, most of them wouldn't came up to a solution thats even similar to the artist work.
"a sepia is just a sepia"
What I meant was that once sepia-ed and saved as a jpg, you can't convert it back to colour, unless you have the original. As a designer, I would rather buy a colour photo and do it myself so I still have two choices. Thats all. I love sepia, but to me its more of an art form.
Regards
P