Followup on the Super IRAs

I just thumbed through the "green book" explanation of the revenue segment of the President's proposed budget.  Contrary to my assertion below, limiting plan contributions once a taxpayer has about $3 million is going to raise an extraordinary amount of money, $800 million in the first year alone!

I would dearly love to see the math on that one.

Remember, the new provision only prevents new contributions once the limit is breached, it does not demand disgorgement or taxation of excess accumulations.

For the sake of argument, we'll assume that those facing the contribution limit lose the right to make a $50,000 contribution, the 2012 limit for SEPs (it's $51,000 in 2013, could be more by fiscal 2014).  I assume that Treasury assumed the $50,000 would still be paid as compensation, and would be taxed.  Let's say the applicable tax rate would be 40%, so this taxpayer will pay an additional $20k in income taxes.

That means that to raise $800 million in new revenue there are already 40,000 taxpayers still in their earning years who have accumulated more than $3 million in qualified retirement plan benefits (all plans and all IRAs are aggregated for this test).  All of them would otherwise make a maximum contribution.  Is that credible?  This small group has $120 billion in qualified retirement plan assets?

Am I missing something?  I must be, because these numbers don't make sense to me.