The author of Psalm 49 is seeing the power of money used against him, through bribes and manipulation. It's a riddle to him, but he comes to the conclusion that as powerful as money is here on this earth, it cannot cross the line into eternity. Death is the great equalizer where we all stand (rich or poor, master or slave, influential or unknown) before God on level ground, and Yahweh himself is the only one who has the power to redeem us from death.