What would I be doing differently if I had one hundred million dollars?
Don't just read the question. Stop, right now, and spend a couple of minutes writing a list of the things you'd do differently.
If your answer is "not much", you're person-bound and not money-bound. You are the rate-limiting factor in progress.1
Isn't that a frightening notion? Of course it's very exciting as well, because it means you're far less constrained than is intuitive - but still frightening and frankly embarrassing, at least to the extent that you're moving slower than you'd like. Part of your brain wants to shed this uncomfortable responsibility, to not see it. The question forces you to see it - the immense practical value of a really large quantity of money is hard to honestly turn away from. It leaves you no retreat along lines of thought like "Well, first I'd need...".
Why 100 million, and not 10 million or 10 billion? The psychologically useful threshold probably varies from person to person, so try on a couple of orders of magnitude in your head and see which is the most provoking. I think you want one with a narrative attached to it - I picked 100 million because that was (roughly) enough to fund the creation of SpaceX through its first successful launch. Empirically, it is a sufficient quantity to make daydreams real.
Note that "enough to make daydreams real" is not by itself a good criterion for picking the number: the Wrights made humans fly, in their spare time, with a few thousand 1900's dollars. For that matter, how much did it cost Faraday or Maxwell to steal the secrets of electromagnetism from the gods?2 The more examples you consider, the closer that number is going to be driven down to zero, where it truthfully belongs.
But you don't pick the number with truth in mind -- you pick it trick your conservative, fear-riddled, simian brain into accepting much higher levels of personal responsibility than it wants to, by shaming it with plausible imagined futures. Truth is the last thing you want here. There's a good chance you have all the resources you need, but the question "what would I do differently if I had the money I already have?" is not only heavily redundant, it's not useful because it doesn't engage your imagination at all.3 You want to err on the side of exaggeration. Pick a number with a story behind it - a number that comfortably dwarfs whatever you have at the moment, but is still both comprehensible and attainable. Then stare at it and soak your brain in the hypothetical, wealthier world until you start to see how much you resemble the hypothetical, wealthier you.4