In relation to who? He sold more than the loveable Frankie Edgar did the very next card after 143. And that was a championship fight with a guy like Rampage on it as well.
So in relation to who? I am not here saying he sells like Sonnen did or like GSP or Anderson.
Try to offer more insight and explanation than just opinions you try to pass off as fact.
Fact: The average PPV draw is 474K
Fact Diaz fount in UFC 44,47,49,51,53,57,59,62,65,137,143, & 158
Fact: PPV pays outs:
44,47,47,49,51,53 - unknown
57 - 400K (Couture/Liddell)
59 - 425K (Ortiz/Griffin)
62 - 500K (Liddell/Sobral)
65 - 500K (Hughes/GSP II)
137 - 280K (Penn/Diaz)
143 - 400K (Condit/Diaz)
158 - 800K (GSP/Diaz)
Average payout for UFC PPVs nick fought in is 472K
472K is less than the average of 474K.
So Nick Diaz, at best, even if you give him full credit for drawing the full 800K in 158 and believe that GSP (who draws that number even when he fights a can) drew no one, still draws a bit less than average ... where 'average' = the average of what all PPVs since UFC 57 (the earliest data I could find, but unless he was drawing 500K for the PPVs before 57, which is highly unlikely, then I expect his average is far less, but I don't think it would be fair to go aback that far.)