FWIW, this is apparent in the data as well---employers are price sensitive, but not nearly as price sensitive as people might think. They good employers aren't stupid and realize you get what you pay for. In fact, the number of one predictor (by far) of who gets hired on oDesk is not experience, hours, tests, county etc.---it's how customized their cover letter is (I took the Levenshtein distance between an applicant's cover letter & their previous cover letter to create a "customization score" that I used as a predictor in a model of hiring).

At least for development work, where each job is only receiving ~10-15 applicants, a well written cover letter that talks intelligently about the employer's problem can cut through the noise of low-quality applicants & lead to a hire.