I had a discussion a month or two ago with the architect on our project. He said that at one time he did a cost comparison, I believe for a client, of metal brackets vs. m&t joinery. You had more money invested in just the brackets than the m&t joinery. Then, you had to buy proper bolts, fit-up and drill all the timbers, and bolt everything together. I've got a fair bit of metalworking experience, and even with automated punches and cutting equipment, there would be a lot of time just making the brackets for a given joint, never mind all the rest.
