Why do you all want to be billionaires?
Money doesn't buy happiness.
It's not everything, but it truly makes every aspect of your life easier. I'm not talking about your materialistic person that's going to spend it all on expensive luxury items, but for a regular person. It can mean a much better family life where you won't have to worry about problems that leads to another.
Money doesn't buy hapiness but it is more pleasant to cry in Rolls-Royce than in old Corsa

.
Seriously as you said it is just for beeing not worried about future, life, familly, food. I would not buy huge yacht, or villa house.
So where is this time machine?
