There’s a WOJ that says Harry doesn’t make money as a Winter Knight because his salary is power, basically...
That makes excellent sense, actually.
Think about Harry's negotiation with Mab: what he bargained for was a healed back, and POWER. If he had included "oh, and enough money for a comfortable living," I doubt she'd have quibbled, nor made the cash hard to collect. But it ... Really wasn't on Harry's agenda when he negotiated. It really, REALLY wasn't.
So it's not part of the deal.