Lacey said Lansky was worth $5-6M at his peak. He spent his last $50k paying for his son's (unsuccessful) operation.
Lansky did not "lose everything" when Castro nationalized the Havana Riviera and the other casinos. Lansky and a group of his investors put up $5 million, along with Batista's $6 million, to build the hotel. Most of the $5 million was put up by Lansky's partners, not him. He later prospered in Bahamas gambling.