On further reflection of the $20 billion puppy, I realize I subscribe to a "The buck stops here" principle. Which is to say, a person is not responsible to seek out and eliminate all suffering. But when a person can stop wrongdoing in a decision that's in front of them, the person is responsible.
The law takes a similar point of view. If someone offered you $20 billion to torture and murder an orphan, and you did it, you're going to prison. It does not matter if you spent all of it to save millions of orphans elsewhere. Your responsibility is to stop the buck when the decision is in front of you.
When you realize that something is an important principle, it becomes increasingly hard to justify ever violating it. It's not your duty to seek out and stop all suffering. But if you integrate the principle that, when a buck is being passed, it must stop somewhere; and that it must stop with you; then violating this principle comes at the cost of integrity. Even if no one catches you, you know what you did. If previously, you did not have to lie to the world – now you do. But if you maintain honesty, then everyone knows that you are for sale. For a big chunk of money, you stepped on a puppy. What else are you happy to do?
Outside of the values we infuse it with, life does not seem to have an intrinsic meaning. In this sense, it is similar to an open-ended video game; a game such as EVE, or like World of Warcraft, which does not have an obvious goal. Your initial purpose is to explore the game. But once you've done that, what's your goal? If you pick one, then whatever it is – it gives meaning and fun to the game. But if you do not choose one, there's nothing; there remains no incentive to play.
So it is with life. There seems to be no intrinsic goal, but you have to choose one for yourself, otherwise it is pointless to live. If you have chosen goals for yourself; and one of them is that the buck stops with you; then violating this has an intrinsic cost that cannot be measured in any amount of in-game currency.
Your goal cannot be to stop all suffering, everywhere. That involves coercion. That is not entirely up to you. But you can make it your goal that the buck stops with you. And that is a principle worth defending.