This seems to miss the point, which is that polyamory is a preference or orientation, not something that women need to be "enticed" into by high status or attractive men.

In many cases, people first try polyamory when they're enticed into it by an attractive potential partner. WrongBot gave an example - "The chance to date a pretty girl, though, can be sufficient motivation for a great many things (as is also the case with pretty boys)" - and I've seen it several times myself.

In many places, enticing previously-monogamous people is a polyamorist's only choice, because polyamory is so rare.

There are significantly more "out" homosexuals than there were in 1850, even if you think homosexuality is purely orientational. Since we're talking about observed behaviour and not personal preferences, social consequences are highly sensitive to social determinations.

That aside, I sincerely doubt this (or sexuality) for that matter, is purely orientational. Consider a very undesirable man who is somewhat inclined towards polyamory in his youth. Because he is undesirable, he's going to have an extremely difficult time actually practicing polyamory. The result will be rather heavy, continual negative feedback. If he tries monogamy, and is relatively successful, he may start to lose interest in polyamory due to the fact that the rewards he is receiving contradict it. A more desirable man may have met with more success, gained positive reinforcement of polyamory, and decided to incorporate it into his identity.

For a non-sexual/romantic analogy, consider the same child born to two different families (or identical twins, if you prefer): a highly functional, wealthy family that strongly encourages him towards "traditional" success of whatever form best fits his skills, and a similarly functional but relatively poor family that encourages him to do whatever his father did and be self-sufficient. If we interview these two children at 21, we expect them to be very different people. They will likely both have very different but firmly held views on what constitutes a good life and what constitutes success, such that each might be miserable in the other's life. This is very much analogous to an orientation, as it is unalterable and not directly in the control of the individual. It is, nevertheless, highly sensitive to local social values and rewards. Some individuals are such that, almost irrespective of their circumstances, they will turn out a certain way - some underprivileged children will find ways to be lawyers and investment bankers, even with inhospitable childhoods, and some children of extremely successful people will regress to the mean despite their parent's every effort, in many cases quite willingly.