Quote:
502.13a Cumulative upkeep is a triggered ability that imposes an increasing cost on a permanent. “Cumulative upkeep [cost]” means “At the beginning of your upkeep, put an age counter on this permanent, then sacrifice this permanent unless you pay [cost] for each age counter on it.” If [cost] has choices associated with it, each choice is made separately for each age counter, then either the entire set of costs is paid, or none of them is paid. Partial payments aren’t allowed.
So culmitive upkeep allows you to choose not to pay the upkeep cost, and if you don't you sacrifice the card.