They can manipulate their system and make us losers and if they can do that we have nothing to do. Gambling on casinos is very risky as if any admin sees a large amount then they can manipulate it though for the small amount they do not manipulate it. And it does not depend on all the casinos. I think blackjack will not do this type of manipulation for only 1k dollars.
You're just making an assumptions, how it's possible the casino can manipulate their system if they give a way to us how to verify each bet using cryptography and the bet is differ from one to another. If you tend to lose when you bet with high amount money and you tend to win when you bet with small amount money, it's just based on your luck and you're not gamble so long when you bet with small amount money.