I'm not an expert in this topic - I've just read a few books and shipping was covered in a few of my upper division classes. They are the most important factor

I'm not an expert in this topic - I've just read a few books and shipping was covered in a few of my upper division classes. They are the most important factors in the context of reliably shipping goods from port to port. If there was a sail technology that allowed reliable transit, predictable speeds and times (really slow is OK, a little late is not), and didn't cause an increase in other costs (say, insurance or maintenance), and could move the tonnage involved (up to 40 tons per container multiplied by thousands of containers, or enormous dry goods loads), I suspect it would capture a sizable portion of the market. Edit: it occurs to me that significantly reducing fuel costs would allow entirely new kinds of loads to be transported and potentially radically alter the world economy. I once saw a chart where the Y axis was price per unit and the X axis was unit density. There was a line on the chart, above which it is economical to ship a good, below which it is not. The top right of the chart had things like electronics - which have been shipped since the dawn of the industry. The bottom left had things unprocessed ore, which have never made sense to ship.