Reducing the cost of $5M+ homes will slightly help some wealthy people who live in NYC, and there will be a modest trickle-down effect into less expensive properties. But I thought the goal was to generate tax revenue from the taxes, which wouldn't happen to the extent they end up in the hands of NYC residents.
EDIT: apparently it hits all homes over $1M, which means it will hit more homes but also won't generate revenue to the extent the homes end up being owned by New Yorkers.