This isn't really and either/or thing to vote on.
Billionaires are inevitable in our economic system.
Also, becoming a billionaire is impossible while treating your fellow man with even average decency.
If someone actually came up with a cure for all cancers, they'd absolutely have an ethical duty to provide it to the masses without cost being an obstacle.
But in this example, that person would have such notoriety and acclaim that they'd make a billion dollars anyway (not to mention any small income from each cancer dosage, with the millions of people who would take it across the world).
