OWD - I don't think you will ever see a more accurate estimate than that given by Salopian.

The take-away from this thread should be that it matters much more what level of workmanship was ordered, paid for, and enforced (QC) than who did it where.

London may have paid better wages, but it had a higher cost of living. If not, all craftsmen would have gone to London --- and they didn't. Then, as today, people have a wide range of reasons for living in any given location.

This is the most difficult point for me. I believe that few craftsmen had the kind of passion for gunmaking that we love to imagine. Then, as today, most found themselves stuck in a job and not at all sure how they got there. Gunmaking paid decent wages for the time and place, not more. Very few got rich in the gun trade.

Best guns came about only by rigirous enforcement of QC standards from a master/owner with his reputation on the line. It came not from the fortuitious assemblage of blessed parts made in a given location or factory. I did come from the demanding supervision of all aspects of his guns by a man who counted his money to the penny.