“Why work?”

Here's a claim, with concrete numbers, that:

"a one-parent family of three making $14,500 a year (minimum wage) has more disposable income than a family making $60,000 a year."

That's after various government benefits and taxes, but the calculation seems incorrect to me.  For instance, should the Medicaid and CHIP benefits of the poorer household actually be valued — to the user — at $16,500 a year?  (Is that number coming from some kind of cost basis?  If so, is it adjusted for the age of the Medicaid recipients to rule out nursing home expenditures?)  Is the $60,000 per year family receiving employer-supplied health insurance?  The assumption seems to be that they do not.

Still, even if you make adjustments this is a scary comparison.  I'd like to see a more exact calculation of the implicit marginal tax rates of the poor, as they climb from say 15k a year through the 60k range.  Does anyone know of such a table?

For the pointer I thank CC.

Addendum: Andrew Gelman comments.