The economics are true of just about anything that scales -- startups and anything in the arts both come to mind. There's no guaranteed route to six-figure comfort (like there is with, say, dental school), but the potential rewards are enormous.
And, as other responses have pointed out, in all of these fields, people really, really want to do them. The number of writing jobs that are 'comfortable' (pick your number, $60k?) has sharply declined from the glory days of the newspaper industry, but it still has the same non-monetary attractions, and there are the still the same opportunities to become, say, a bestselling nonfiction author.
And, as other responses have pointed out, in all of these fields, people really, really want to do them. The number of writing jobs that are 'comfortable' (pick your number, $60k?) has sharply declined from the glory days of the newspaper industry, but it still has the same non-monetary attractions, and there are the still the same opportunities to become, say, a bestselling nonfiction author.