$100m can very comfortably afford a private jet. Maybe not a brand new G6, but a small to mid size jet could be comfortably purchased and maintained while barely spending more than the market appreciation of that $100m.
Pilots and maintenance will cost you $1M+ per year. Depending on how much you use it, that could be significantly more. Spending 10-20% of your net worth on a vehicle up front + 1% pa going forward is not "comfortably afford".
If my net worth was $2M, I would not say that I could comfortably afford a lambo.
Or, fly anywhere in one swoop with a less than 10 year old Citation CJ4 or similar that will run you less than $6m and seat 10 passengers. And the annual operating costs will not get you anywhere close to $1m. Even a G650 isn't going to run you much more than $1.5m annually unless you are putting a ton of hours on it.
But I will also say that 10-20% of your net worth (wouldn't be up-front, it would be financed.) is not that big of a deal when you have a huge net worth. It's a lot when you make just enough to survive. It's not a problem when you still have enough left over for several lifetimes of comfortable living. Just depends on your priorities.
I agree that chartering is usually a better way to go. But private jet life is comfortably affordable at a $100m net worth. Maybe not private-jet-life, and mega-yacht-life, and rare-original-art life all at the same time. But you could definitely choose one or the other.