]] Can someone explain what John means when he says "her life cannot be worth half that purchase," as he is talking about a 40-ish woman? Is he just going with the flow of Fanny's conversation (I am assuming he can't really mean what I think he means)?

] I think that's exactly what he means--that she could not be expected to live until age 55! or even to age 50 if he literally means ' half that purchase'

I'm mulling over a different interpretation, but one which makes John even more of a rotter. I haven't quite thought it through, and have trouble formulating it, so please bear with me. :-} I'm thinking that John could be referring to the value of his step-mother's life to him and Fanny. The thought of Mrs. Dashwood living another fifteen years or more makes him realize that this woman cannot be worth that much to them. Could it be that he is, in fact, worrying that Mrs. D. would "live for ever", and that paying her an annuity for fifteen years or more is more than she is worth? He is a cold-hearted git, after all, and Mrs. Dashwood is only his step-mother. Am I making any sense?