The anthropological idea is that generosity, gift-giving, expenditure, prestation, conspicious consumption, conspicuous destruction, is a signal of what the spending hand that always poureth out can afford to waste or destroy. If you don't have to ask (or to pay attention), that proves you can afford it.
Why advertise your studied indifference to cost? Because (as Veblen said) such an advertisement announces status. But status-seekers in gift economies originally and logically also seek the benefits of status: the tribute of those below them. So gift-givers expected returns on their gifts, expected those they benefited to repay them with interest. (Marcel Mauss explicitly saw credit and interest as prior to barter and equivalent exchange.) And yet such an expectation immediately blights the idea that the gift is a gift. It becomes a loan instead, one perhaps unwilllingly accepted (though the unwillingness would be part of the point the lender seeks to make).
So what do the truly great do, those who don't want to blight the generosity of the gift? They don't give gifts - they give metagifts. They destroy their wealth instead of putting others under an obligation of gratitude or return by giving them that wealth. We don't owe the truly great anything, because they didn't transfer their wealth to us: they didn't want to oppress us with their largesse. That's how great they are: they didn't need to buy our loyalty, at terms however generous.
I make this point to show one version of the recursive aspect of human mind-reading, of assigning motives to others, including their motivation to assign motives to you, toggling back and forth in an endless rock, paper, scissors or Dupinian whirlpool.
Part of what's interesting about costly signaling, when humans do it, is its recursive quality. You won't really find that among any other animal; the human version says a lot about how central are nested levels of mind-reading to how we interact. This is particularly true when it comes (as with the potlatch) to self-reflexive signaling, that is to say to signaling our attitudes toward our own signaling.
A neat paragraph in Balzac makes this point: La Cousine Bette describes a certain kind of competition, occuring at a party, where the beautiful courtesanes try to outdo each other:
This is pretty straightforward but deserves a second look. Each woman is dressed expensively, to set off her costly beauty. Each therefore is declaring herself simultaneously both the prize and the quality for which the prize is given (the French "prix" covers both prize and price, which is the point). The way to understand this is that each woman is a prize her erotic partner displays to advertise his value (his status and power), the value thus established then redounding upon the value of the woman who's been chosen by so high-valued a man.
Une partie est toujours pour ces dames un Longchamp de toilettes, où chacune d'elles veut faire obtenir le prix à son millionnaire, en disant ainsi à ses rivales: - Voilà le prix que je vaux!
She thus becomes a sign of her own value, because the millionaire she's with values her, and her beauty signals that he matters and so his valuation of her matters. He's only there as a toggle (well Balzac's a realist, so he has to supply the diamonds and pearls too, but they're only there as toggles as well) so that she can become a signal of herself, can become her own signal.
Variations and further complications of such situations (sexist though Balzac's scenario is) exists passim in human societies, making it impossible to disentangle signals and what they signal, "until we cannot tell apart / The idea and the bearer-being of the idea." Thus the Derridean idea of the sign, suitably understood, is not very far from what you'll find in evolutionary game theory.
It also makes possible certain ways of understanding the systematic manipulation of the interpretation of signals: Marx says capitalism depends on the carefully established confusion of labor and labor power. Let's say that labor power signifies labor (I sell my labor power to you, but you obtain my labor and the surplus value of their difference: you get my labor but pay only for my labor power): the fact that things can signal or signify themselves, with the circuit of signification routed through a second or third party, opens up a gap, an internal difference where the meanings are, and where they can be argued about.
I think this is what de Man and Benjamin mean by allegory: a thing that exists only as its representation. Turns out this idea is in Marx and in Darwin (in germ, in his theory of sexual selection) as well. But you won't find it in the Literary Darwinists.