Kind of late, but it's probably do to the fact many WWI or WWII collectors (and possibly "purists") consider Weimar-era lugers as just a small commodity. Where as those "every WWI or WWII produced weapon" luger had to see a battle command high prices (or as high as our economy will allow

), the history of both the Weimar Republic and what was produced in that era are but a footnote in history and known only as Hitler's Beer Hall Putsch and Kristalnacht. :P
What's not understood is what happened during this era...hyperinflation, the hatred, Treaty of Versailles. For instance, the luger I have was "dated 1921" but was actually made in 1924. What they did was use the same markings albeit one other that would indicate production year. This got around the arms reduction of the Treaty of Versailles and they produced weapons such like such for years! When I saw it in a case for $600 at the busiest gun show of the city on Sunday, I couldn't believe it. Either people missed it or didn't care. But when I saw one say "Wow a luger! ...oh..this thing isn't "real" I about cried. Offered 500, he took it, it's the 2nd pride of my shooters today.
Sorry, type more than I talk!