Hang on. Why not go back to prevent your own birth?
If you're successful then you wouldn't be born. And therefore couldn't go back.
Don't the people with the $1bn realize this?
Of course. Just because they offer the money, that doesn't mean they actually intend to pay it out.
But that's what the money is for! If they don't want to do it themselves (for whatever reason), then they offer compensation to someone willing to do it in their stead.
If they're not willing to risk themselves for their own theories, they're cowards and lacking in ethics.
Play out the scenario in your head. You go back, you do the deed. What happens from that point onward from your point of view? You cease to exist? You and the universe you are in cease to exist? That seems rather odd for a thing to happen, it seems it'd be far more likely that you'd continue to exist and reality would in some way and some how fix itself to get rid of the logical paradox. That's just a guess, but that's where I'm coming from when I say "I'm pretty sure I'd continue to exist if I did this"
Have you ever read Robert Silverberg's novel
Up the Line? The main character is told that while he is in the past, he has free will to do whatever he wants (subject, of course, to Time Patrol monitoring; if he commits timecrime, they might just show up out of the blue and arrest him even before he does it - from his pov). He can talk to the locals, eat a meal, observe historical events, etc. If he were to commit timecrime by eliminating one of his own ancestors, he wouldn't immediately blink out of existence
while he was in the past. The theory put forth in the novel states that 21st century time travelers (the story takes place from the pov of the years 2058-2060) are protected by the Benchley Effect so that they continue to exist until they reappear in the 21st century. At that point, they
will vanish because the moment they eliminated their ancestor, they will have ceased ever to have existed in the first place.
Pretty neat trick for somebody who is imaginary at best and non-corporeal at worst.