Grey market, not black. It's been several months since I've talked to anyone in the space but full-chain reliable quiet Chrome exploit packages were high six figures, with discussions starting about bugs reaching 7 figures imminently, and the people I talked to might have been talking that down (or talking it up).

Again, remember that grey market payouts are tranched, so you could get 3x more than Google would pay, or you could get 0.5x, and for much more work.