I don't want to measure the cost, because we all know that we are working for less than "minimum wage" (whatever that is nowadays)...
The way I look at it is that we are creating heirlooms, whether for our family, for our community, or for fellow quilt-lovers, artisans, the quilting heritage. Just think of all the great quilts you have seen, at museums, online, at quilt shows, etc...
I bet that when some of these pioneer women were sewing by hand, in cabins, covered wagons, etc. that none of them thought that they were creating history and adding to the cultural legacy of our great country. We are doing it for the future.... and that is why we keep sewing one more stitch, even after midnight!