I speculate that some signals gain their effectiveness from being costly, while others gain their effectiveness from mere association with costly signals. Telling a boss that you got a college degree in order to signal to the job market that you would be a good job prospect is not likely to hurt your chances of getting that job. But, telling potential mates that you dress nice to increase your chances of sleeping with them, but have to keep an eye out for deals and frequent thrift shops to maintain your upper class dress style, will not, ceteris paribus, increase your chances. (Obviously this depends on the particulars of the individuals involved in such a discussion, as this would probably not apply to many LessWrongers who could be aware of signalling and find your optimization thereof inherently attractive.)