But the point I want to make is not about the prices. It is about why do audiophiles not know Hoelscher.
Ludwig Hoelscher was in a Trio founded by Elly Ney (piano) and a violinist. Ney was an active member of the Nazi Party. Don't know about Hoelscher, but the trio performed in Berlin during the war years. Don't underestimate the impact of that association, particularly in post-war Europe particularly in the '50s. Don't know if that is a reason that audiophiles or non-audiophiles do not know Hoelscher but it probably is. Popularity has a context.
The same may be true for East German conductors - the DDR wasn't keen on losing conductors. It took time for some to gain/regain recognition. Sanderling, Fricke, Kurt Masur ended up at the NY Philharmonic, and others.
Edit: To further the point ... Joseph Keilberth, the very conductor of the Hoelscher album of which Tang posted a picture, was kicked out of Czechoslovakia at the end of the war, perhaps spurred on by the Soviets. Regardless of musical talent, during that time many Germans were shunned by countries around Germany.