This could be easily explained in a lot of ways. Here's an example that makes sense intuitively to me: popular conception of Oracle among Bay Area locals I know is that they are money-grubbing assholes (similar reputation to an investment bank or something). They may attract a set of applicants that will negotiate aggressively and only accept high salaries. I'm white and I can sure as hell say I wouldn't work at Oracle for market rate. This effect may be correlated with race due to the way ideas travel through social groups, and immigration status.

I think this is at least as plausible as "bias" to explain why white applicants would be hired less and paid more.