the Stooges and Velvet Underground are legendary rock-bands who only sold a few thousand copies while active. Sun Ra and Ornette Coleman are legendary jazz-artists who even by jazz-standards weren't popular at all.

Now that I think of it, Miles Davis 60's albums with the Wayne Shorter-Hancock-Williams quintet sold in the range of 20000-30000 copies each, at a time LONG before illegal downloading.

And in Hip-Hop, isn't Ultramagnetics "Critical Beatdown" a legendary album and them a legendary group? That people argue this is proof of how pop Hip-Hop has become...