You may want to append a zero. ;) Mintage of that piece (1 Pf 1990) was 15,673,600 ... Other 1 Pfennig coins with low mintages (1972, 1973) are similarly expensive. Whether they were melted down, I don't know.
By the way, the GDR replaced its currency with the DM (the Federal Republic's currency) on 1 July 1990. The country did not join the Federal Republic of Germany until 3 October 1990 -- and the GDR pfennig denominations (1 Pf to 50 Pf) even stayed in circulation, in the Eastern states, until the end of June 1991.
Christian