I think that I read somewhere that Kramer won his money gambling.
Kramer's money
S08E12 The MoneyretroNov 7, 199670 days before it aired2 posts by 2 posters
🧩 Trivia
Fans discuss how Kramer obtained the money featured in "The Money" episode, with one recalling he won it through poker before the AIDS Walk.
2 posts
He plays poker before aids-walk