How come in most cases welding is considered the lowest cost joining method?

The reason why I ask this question is because; I'm trying to broaden my scope of learning in welding. I do have an answer for myself but, I wouldn't mind hearing some else's information. Easy Ten Points.How come in most cases welding is considered the lowest cost joining method?
well, consider how well the two pieces are joined together. The only way to get a connection as secure as that would be in special situations where you can use a super powerful adhesive. In some situations one of the two pieces glued together will fail before the joint will fail. But these kinds of adhesives are expensive and can be difficult to handle. Now consider welding, Its an exceptionally secure connection at a relatively low cost and does not take too long to do as compared to other methods such as bolting and riveting. Which require the material to overlap and have holes made. Then there is the cost of the mechanical fastener itself. I imagine that a foot of weld costs less, in materials labor and utilities, and is stronger than several bolts would be.How come in most cases welding is considered the lowest cost joining method?
I suppose the guy in the above is correct, but make no mistake, welding can be damn expensive. Especially when it comes to welding up a pressure vessel made of 40 mm plate. I've observed this and the weld preparation alone (grinding v's on the plates to be joined) can take longer than a day. I suppose all is relative.