The economy of action

"Plenty of people wish well to any good cause, but very few care to exert themselves to help it, and still fewer will risk anything in its support. 'Someone ought to do it, but why should I?' is the ever reechoed phrase of the weak-kneed amiability. 'Someone ought to do it, so why not I?' is the cry of some earnest servants of man, eagerly forward springing to face some perilous duty. Between these two sentences lie whole centuries of moral evolution." -- Annie Besant

"weak-kneed amiability" or economical thinking? Doesn't it all come down to cost benefit analysis. How does the economy of "risking everything" work?