This a devil's advocate question, because I don't know of a study/data to directly answer this comment on skeptics. However, I cannot reraise that as a question there because I can't find any notable source making such a claim.
Off the top of my head, it seems a bit silly to assume that police can more easily identify someone's socioeconomic status (SES) than his skin color, but there may be other mediating factors at play, such as neighborhood etc. There is in fact one hypothetical story on Gawker that seems to follow the same line of reasoning, even if just implictly:
Let’s say you’re a teenaged black male living in public housing in an impoverished neighborhood. Your local public schools are far inferior to those in wealthy neighborhoods, and you’re financially cut off from private schooling. Without a good education, your opportunities for economic betterment are few, so you turn to selling drugs. Because drug enforcement across the country favors arrests in poor and nonwhite communities, you’re arrested outside your apartment. You become one of the 30 percent. [...] Eventually, you go back to jail, and as a repeat offender your chances of a felony conviction are higher. The process repeats itself.
Meanwhile, the white college senior across town has been selling coke to partygoers for his entire four-year tenure. The cops don’t patrol his dorm building like they do your housing project, and they don’t make Terry stops in his upscale neighborhood like they do in your ghetto. You’ve committed the same crimes, but he never encounters the police, never gets wrapped up in the criminal justice system. You are one of the 30 percent. He is not. He goes on to become a doctor, a lawyer, a banker, a cop.
So perhaps the question whether racial profiling is better explained by the SES of the suspect deserves a more serious look/answer.