In this case the only reason the money pumping doesn’t work is because Omega is unable to choose its policy based on its prediction of your second decision: If it could, you would want to switch back to b, because if you chose a, Omega would know that and you’d get 0 payoff. This makes the situation after the coinflip different from the original problem where Omega is able to see your decision and make its decision based on that.
In the Allais problem as stated, there’s no particular reason why the situation where you get to choose between $24,000, or $27,000 with 33⁄34 chance, differs depending on whether someone just offered it to you, or if they offered it to you only after you got <=34 on a d100.
That’s beside the point. In the first case you’d take 1A in the first game, and 2A in the 2nd game(34% chance of living is better than 33%). In the 2nd case, if you bothered to play at all, you’d probably take 1B/2B. What doesn’t make sense is taking 1A and 2B. That policy is inconsistent no matter how you value different amounts of money (unless you don’t care about money at all in which case do whatever, the paradox is better illustrated with something you do care about) so things like risk, capital cost, diminishing returns etc are beside the point.