Boy, the Summarit 50/1.5 is subject to many condition issues. It is extremely subject to internal haze, sometimes it can be cleaned, often it can't. Like the Summar, Summitar, and collapsible Summicron, it has super-soft front glass (flint glass -- lead crystal), so it is very subject to cleaning marks. Further, the coating is Leica's early soft coating, which is also very subject to cleaning marks, or even being completely cleaned off the lens.
So the price realized is highly variable, depending madly on condition. From $100 to $600.