You just have to stick to legal, regulated online casino sites such as BetMGM, Caesars Palace Online Casino, FanDuel, Betway, bet365 and BetRivers. They offer great casino game ranges and they will pay out quickly and without any issues if you win.
Diamond Casino Heist Payout: $10.34 - $11.37 Million\n\n The Diamond Casino Heist payout is by far the highest in GTA Online. The rewards for the mission add up to $10.34 million on normal difficulty, and it can go up to $11.37 million, if the heist is on hard difficulty.