For animal weapons to be honest signals, they must be expensive—exorbitantly expensive. So expensive, in fact, that only the top-condition males can afford them. Costs keep signals honest. If anybody could afford big weapons, then all males would have them, and differences in weapon size would be meaningless. Only when most males cannot possibly afford them will big weapons provide reliable signals of fighting strength. Then, and only then, will it pay for males with small weapons to walk away.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 601