The art of estimating is not just the time it takes to cut a mortise and tenon. It is timber movement, efficiency, bathroom breaks etc. I have found that the more people working on a project the more man hours get billed to a project. It is not that any one person is not holding his weight. I think it's more starting and stopping to shuffle materials as work is completed. A one man shop will cut a frame with about one third less man hours.

Kevin