Yeah, the reason 50% equity is the answer for "any" bet is because bets are matched 1 to 1 and therefore, no matter how deep the stacks, the worst pot odds you can get is 1:1 or 50%. You can get 1:1, 2:1, 3:1, etc on your money, but never 1:2. The first number must be greater than or equal to the second number.