I would argue that any musician active at the time will know someone who was as good as Led Zeppelin, but never made it because they couldn't get a label contra

I would argue that any musician active at the time will know someone who was as good as Led Zeppelin, but never made it because they couldn't get a label contract at the right time. This is particularly true if you include black artists. It's not just marketing - production costs were very high. There is an element of cargo-cultism in the boomer experience, as a result of scarcity and strict gatekeeping that lasted pretty much all the way to the early 2000s.