This achievement goes hand and hand with "KaChing Bling", so refer to that achievement regarding information on how to get it.
Once one of your songs reaches multiplatinum, you will easily have several millions of dollars to play around with. Go to the Jeweler, and buy as much jewelry as you can. All jewelry you have increases how much style you get after each fight, even if you're not wearing it.
After buying as much as you can, go and do a fight. If you've bought as much as you can, you can easily get well over 800k style points in the single fight, netting you the achievement.