The phrase means something is completely impossible to get, even with the greatest effort or best incentive. Front row tickets to the final game are not for love or money at this point.
Pro Tip 2/3
Emphasis on Desperation
It's often used to show someone's desperation or strong desire for something they can't have. He wanted the collector's edition comic book, but it wasn't available not for love or money.
Pro Tip 3/3
Intangible Rewards
'Love' indicates non-material incentives, meaning it's unobtainable for any personal favor or connection. She couldn't secure a spot in the course not for love or money.