Lol! Yes, obviously I DO understand that not all great artists sell a lot of records. However, Neil Young has sold quite a few. This is perhaps something else of which you needed to be made you aware:
Album sales figures for Neil Young according to Rolling Stone's 500 Greatest Albums Of All Time:
After The Goldrush - 2.5 Million
Harvest - 4.3 Million
Tonights The Night - under 500,000
Rust Never Sleeps - 1 Million+
Everybody Knows This Is Nowhere - 2.4 Million
This doesn't even include his records with Crosby, Stills and Nash. Altogether he's sold about 17.5 million records. Not exactly mediocre.