Cost makes signals credible.

https://en.wikipedia.org/wiki/Signalling_(economics)

https://en.wikipedia.org/wiki/Costly_signaling_theory_in_evo...

This is getting way into the weeds but the fact that costly signals are more trustworthy doesn’t mean all signals are costly.

An “in this house we believe” sign is signaling but if you live in a liberal neighborhood it’s extremely low cost by all measures.