There ccan't be parity, but the system allows for those few to join up and play on the same team because there is a cap on individual salaries. If Miami or LA can offer 20 mil a year and Milwaukee is offering that same 20 mil, where are the Lebron James type players going to sign? Milwaukee is stuck with whatever near-star player they can get - and they have to overpay for that player, setting them even further back.
But Stern is happy with Boston, NY, Miami, LA, and a couple of upstarts fighting for the titles every year.