I suppose it would all depend on the size of the the workshop,how well equipped it was and how skilled and efficient the work force is,someone working on his own with minimal equipment could not possibly give the same work output as a well run well aquipped set up.For example,a workshop with large three phase machines would machine far quicker than a one man band with small saws and planers etc, there cannot possibly be a fixed rate unless you are comparing like for like.You need to assess the workers worth,I would not expect to pay an apprentice the same rate as an efficient well qualified tradesman.Ive met tradesmen who aren't worth tuppence working in rubbish workshops and they are definitely not worth paying £200 .