I know of two people that sharpen knives/scissors in my town. One is the guy who visits my LQS every Wednesday to do machine repairs. He charges $1 per inch I believe - very cheap. The other is at the farmer's market downtown and are there about once a month. They are more expensive. Both sharpen onsite and return the items that day.
I think it would be a good idea. I don't know how busy he would be, but if he went to each fabric store and arranged to do the service once a month, that would be nice.

