Suggestions for/Where to start with Silver/Bronze Age

DC and Marvel are both bad where some big collection in a series will go out of print, yet this volume is not available and used market are crazy expensive. There are plenty of Omnibuses or series books like this in both their catalog and in some ways Marvel is worse about it as they don't have the back list warehousing like DC, which has kept many, many collections always in print.

Marvel has had much better luck getting the greater proportion of the old 60s-70s super hero stuff in reprint at least once, but they never stay in print. DC's reprint on books is madly inconsistent, but on some later modern series like Vertigo and others, they have been a big part of the the whole trade reprint business existing. Those series trades are why there is that kind of business now, as they kept popular series in print comic back lists going.

As a reader, the one that is out of print and insanely priced used is Essential Thor Vol. 4. That thing must have had a short first print run and it never has been reprinted, yet volumes before it and after it got a second print. The goofy thing has been going for like $80+ used for probably 5 or 6 years. Don't know if many are being sold at it, but it's one of the few Essentials that I don't have.

And worse on it is the Thor that it's kind of been reprinted around in color too. I think with the last Thor Omnibus that came out finally got it out as the Masterworks was two copies, one of which was also out of print and crazy expensive.

Keep an eye out for the Epic collections. The lack of rationale behind the order of their release is a little maddening, but they do seem committed to getting most of their main titles reprinted in full. Although that might mean waiting five years for them to get around to the volume(s) you're looking for. But I know the Black Panther Essential volume was another that became prohibitively expensive and they've already Epic-ized that material.