Minority set asides require that a certain percentage of contracts should go to minorities. But competitive bidding is still required. A higher bid might be accepted if the bidder is a minority and the bid is close. But the bid isn't just given without bidding or notice.
There are a lot of set-asides which are essentially non-competitive within the set-aside group, and definitely not competitive outside the group. I don't think you believe that set-asides for race or gender aren't subject to manipulation and cronyism any more than I do.
My tongue-in-cheek point is that the direct nepotism of the mayor is worse than the usual set aside, but not entirely different. He has abused his power by essentially giving non-competitive contracts to his cronies. In set-asides, the law does it for us by limiting competition--sometimes to very small groups of non-competitive bidders. Both are anti-merit and anti-competitive, and both steal from the public pocket.