No need to prevent, just tax more. Then what would happen is that the government would have more money to offer life quality to the people that worked for that billionaire get that rich.
A wealth tax would be nice, instead of income or expenses taxation. Tax those who hoard. If a billionaire is spending $800m on things, he's doing a lot of good for the economy, probably more than taxing him $10m would.
I think it is more fair to equalize power and avoid people being capable of manipulate too much of the society with their money. If the tax is progressive at some point you will have a hard cap of 100% tax.