How many generations of Yosh pipes are there?
The hand-bent pipes were each custom-built by Pops back in the day when his operations was just getting going, I can't imagine too many were made w/ all the time involved. He also made them for Z1's, GS1000's, CB500/550's and demand was probably overwhelming, with race teams in line 1st. I remember ordering a Yosh pipe in 1977 for my CB500-4, it was $550 in advance from a dealer in NY. After a few months of waiting, it never arrived and I got a refund. Machine-made sets were a 2nd option around that time and stamped out much faster. But not as desirable or hard-core.
I found a hand-bent Yosh pipe for a Z1 hanging in the rafters of a shop 2 years ago, I put it on ebay and it went to Japan for big bucks.
Hearing these things unbaffled is incredible (and absolutely deafening- completely over-the-top and scary). The sound actually changes pitch as it goes on the pipe, literally.