[Nick Zwar]

The John Williams concerts, live in Berlin, Vienna, etc., are actually available directly from Deutsche Grammophon. (And vendors like Amazon, JPC, etc)

Deutsche Grammophon: John Williams Live in Vienna

I guess it becomes trickier these days to pick them up used, especially if you’re looking for something specific, as far fewer copies are produced and sold these days, so the ones who buy them really hold on to them.
Years ago, people dropped their CDs by the boxload at second hand stores or replaced film soundtracks with expanded releases, but that happens far less nowadays.

Shipping alone usually costs more than $10.-, so I don’t know how a store that sells CDs for $10.- and offers worldwide free shipping could stay in business. They’d give the CDs for free basically, and probably even pay on top.