He 'profited by' his experience/mistake. [=he learned something useful from his experience/mistake]
The book can be read with 'profit' by anyone who wants to understand how the system works.
We sold the house 'at a profit'. [=we made a profit when we sold our house]
(..) They have screwed us on student-loans, so we can never get out from under. Then this guy, walks into my office and says: "Those same banks got greedy, they lost track of the market" And i can profit off of their stupidity Fuck! Yeah! I want him to be right! I mean, how come you don't hate this guy? (..)2015 The Big Short
(..) So the banks started filling these bonds with riskier and riskier mortgages Thank you Hendry That way, they can keep that profit machine churning right? By the way, these risky mortgages are called: Sub-Prime. So... whenever you hear sub-prime... think: Shit Our friend Michael Burry found out, (..)2015 The Big Short