6 mana for a 9/9

Cumulative upkeep—Put a -1/-1 counter on this creature. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

At the beginning of your upkeep, remove a -1/-1 counter from each creature you control. Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)