How else do you explain the sales figures still being reported from Billboard regarding how much Jackson music is moving even now? From June 29 through July 05 (Billboard uses SoundScan to capture data on a Monday to Sunday calendar), Jackson's solo catalog moved 800,000 copies in the U.S. alone. That breaks down to roughly 650,000 physical albums and 150,000 downloaded albums.
SoundScan also reports Jackson owns the top album spot this week with Number Ones, and he holds the top two spots on Billboard's Top Comprehensive Albums chart with Number Ones and Thriller.
Jackson died on a Thursday, so posthumous sales the week of his death really only account for sales made Thursday evening through Sunday night, yet he held eight of the top ten spots on the Top Pop Catalog Albums chart. This week, he has captured all ten spots at the top of that chart. (Numbers one through six and eight through ten are solo, number seven is a Jackson 5 album.)
Despite the fact that I'm amazed so many people didn't have Jackson's music in their collections already, and even more amazed at the shot in the arm Jackson's death has meant to the sales of physical albums, I don't understand how you make a case for his cultural insignificance. I would argue that his last relevant album was 1991's Dangerous, but culturally his entire musical output, his position as a fashion icon, and the freak show quality of his both his celebrity and personal life solidify his relevance.
The holy trinity of '80s pop, consisting of Jackson, Madonna and Prince, will always have cultural relevance as well, regardless of child abuse scandals, adoption problems, or record label lawsuits.