Billionaires, as a class, are likely already spending that much or more on lobbying for lower taxes. Or really lobbying for the status quo, since existing loopholes allow them to achieve an ultra low or even 0% effective tax with alarming regularity. The threat they make is wealth flight. "If you raise our taxes we'll take all our wealth somewhere else!" As a result taxes on the ultrarich have essentially been a global race to the bottom for decades. At least now there finally seems to be some indications that wealth inequality cannot be ignored the way it has been for so long. My hope is that we'll eventually see some international framework that effectively raise the tax floor for the 1%. It won't cover every nation, but if it encompasses the EU, US, Commonwealth and other aligned countries then that would go a long way.