Frank Matthews and the other black gangsters made a ton of money during that period, and mostly likely more than any one mobster. They were basically flashes in the pan though, because they didn't leave that generational wealth that set their families up. Take big Paul Castellano for example, he made a fraction of what Matthews and Barnes made, but he was able to set up his kids in businesses, and all are living comfortably as far as I know. Those Harlem guys never were able to take their drug earnings and turn it into something legit that could be used to make them and their family money in the long run.