>If it were possible to accurately forecast cost and revenue, then everyone would start a profitable business, right?
that doesn't follow: it's just as likely if you could accurately forecast cost and revenue, then you wouldn't start many businesses because you'd know they wouldn't be profitable
Both of you get to the same place: if it's possible to accurately forecast cost and revenue, then all the businesses started by people who can do that will be profitable.
And there are so few serial entrepreneurs in existence that we have the following pair of conclusions:
A. It isn't very probable (we are mostly seeing survivor bias)
B. People who can do that start exactly one business, which is sufficiently profitable that they never bother to do it again
Both of these conclusions lead to the situation that picking a serial entrepreneur to invest in is just buying a lottery ticket.
that doesn't follow: it's just as likely if you could accurately forecast cost and revenue, then you wouldn't start many businesses because you'd know they wouldn't be profitable