If you are selling a 0-day exploit on the black market for 7 figures, I am pretty sure you are already accepting that it is being used for evil and not bettering the world.

Not only that, but imagine how many services you and your family and friends use that could be compromised? It could end up costing you unless you and your family pull out of all your online services.

The ultimate irony would be if your bank(s) got compromised by your but and some of your money was lost.