Is that a direct quote? I got a very different impression from the article. It seems they are looking more at a societal level. The women can still be exchanging sex for resources, even if they are the ones desiring sex. For example, it's common for a woman to flirt to have a man buy her a drink, pay for the uber, etc. So while they ultimately want sex, they know they can get sex plus some other resources.
Obviously this can even be the inverse in individual interactions, as their chart eludes to for what lowers or raises the price (age, attractiveness, etc). Just as their statement about there being no value to male sexual favors is only true at the societal level (maybe not even then) and not the more granular one.
>The analysis of sexual interactions as social exchange, with sex itself as a female resource, appears capable of supporting a broad range of testable predictions. It is also a potentially useful link between nature and culture
Also, apparently the male to female ratio on online dating sites (in the west) is 100 to 1. Evidence that access to woman is a limited resource in high demand.
Is it that you no longer demand sex because you're over 40, or women are demanding more? I suspect in any case the women are interested in more than just sex most of the time, unlike many men.
IMHO this is overstated considering the rise of the childfree "movement".
The paper is purely theoretical and not based on any empirical data. So wild claims and exploratory discussion are par for the course.
The dynamic changes a lot with age. Women in this age bracket - especially if they want kids - are of course not in a position to be nearly as selective as they were able in their early 20s.
I'd add, I think there are "communities" (not geographies, but social groups) in which a lot of this holds true, and echoes through society (sex sells) but as a heterosexual male in his 40s, the "women are the suppliers, men are the demanders" narrative is not my experience outside of shallow situations (even if it can be a shallow characterization of, say, the dance floor at a bar)