I'm not in the same intellectual position as you business types, but let me put a spin on this you might not have considered.
You are looking, as did the respondent only at one dimension, one facet of her viability as an investment: her looks. Yes, this is an important aspect, but not the only one.
Flow-charting this, or bar-graphing it would be difficult. Here's where I see this asset could actually appreciate. Oh, and granted she was selling herself mainly on age and appearance, but note that the respondent didn't address her class, education etc.
1. Education. If she has a good mind (and judging from her prose, she does), her educational level will increase. This can be valuable to the investor.
2. Sexual skills. If she's interested in sex and enjoys it, her skills will only improve with time. I have had sex with women in their sixties and seventies, and believe me when I tell you all that you don't know what you're missing. If you're only concerned with looks in a sex partner, you might as well buy an artificial vagina or blowup doll and keep your eyes fixed on a porno mag or movie while you masturbate.
3. Her family's assets. She may well inherit. Is her daddy/uncle/grandfather rich? She could, even without a career bring something to the table here.
4. Kindness. A wife does more for her man than sex, including caring for him when he's ill. If we marry a much younger woman, chances are almost 100% that one day she'll end up literally wiping your ass.
If you think about it, there are many assets that she could bring to a marriage beyond her youth and looks.
Look, I'm no investment wiz, but I do read the prospectus carefully beyond looking at the earnings record of the stock or fund in which I'm interested.
