Maybe security places too much emphasis on the second syllable of ‘wedlock’.

Buying her security — I don’t know. Security is a long term, and not very sexy thing. Their relationship sounds very unequal, and I’d have thought unstable. Not that (as far as I know) I’ve ever met a millionaire. Perhaps impoverished heroines are what millionaires are looking for… someone with whom to share their millions unstintingly… Maybe I’m just an old cynic.

Also security makes me think ‘maximum security’, as in prisons.

Pet, the story is a fairly standard “impoverished heroine swept off her feet by millionaire” one – I assume what is bought is…her…

…

You know, that’s actually a very good question. He buys her…security? Maybe that’s the idea? I don’t know. I’m not sure the publishers thought the title through all the way.

(And the heroine is bought by a young, sexy man’s gold, because otherwise it wouldn’t be romantic.)

A bizarre and unpleasant example of valuing virginity comes to mind. An ex-partner’s uncle owned a pedigree bitch who conceived a litter of non-pedigree puppies. There’s nothing remarkable about that, except that — my ex-partner told me — the uncle had the poor creature put down, in the strange belief that sex with a non-pedigree animal ‘spoilt’ a pedigree bitch.

http://en.wikipedia.org/wiki/A_Bird_in_a_Gilded_Cage

And her beauty was sold,
For an old man’s gold,

Bought and sold are, after all, the same transaction viewed from different perspectives. I assume that the beauty of the ‘Bought: Destitute Yet Defiant’ heroine was not bought by an old man’s gold.